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by state contract, and any devia¬ 
tion therefrom shall be reported 
to your County Superintendent of Public 
Instruction, or the State Superintendent 
at Nashville. 



Class 0^ 3 L 
Book C •' 

if 0 Q 

Copyright N° 7 


COPYRIGHT DEPOSIT 











LIPPINCOTT’S PHTSIOLOGIES 


THE SECOND BOOK 


ANATOMY, PHYSIOLOGY 

AND 

HYGIENE 

OF THE HUMAN BODY 


BY 

J. A. CULLER, Ph.D. 

PROFESSOR OF PHYSICS IN MIAMI UNIVERSITY, OXFORD, OHIO 



PHILADELPHIA AND LONDON 

J. B. LIPPINCOTT COMPANY 





U O* <A 


Copyright, 

Copyright, 

Copyright, 


1904, by J. B. Lippincott Company 

1905, by J. B. Lippincott Company 
1909, by J. B. Lippincott Company 


\ 


We, the undersigned, have carefully read Book II. of the Lippin¬ 
cott Physiologies, and are happy to note the full and adequate teaching 
of the physiological reasons for obeying the laws of health, including 
those that relate to the nature and effect of alcoholic drinks and other 
narcotics upon the human system which this book contains. 

The truths taught are well told in language adapted to pupils in 
elementary schools, for which we heartily recommend the book. 


Mary H. Hunt, 

Life Director of National Educational 
Association; National Director of Bu¬ 
reau of Scientific Temperance Investi¬ 
gation, and World and National Super¬ 
intendent of Department of Scientific 
Temperance Instruction of the Wom¬ 
an’s Christian Temperance Union. 


Members of the Text-Book Committee 
of the Advisory Board 

George W. Webster, M.D., 

President of Illinois State Board of 
Health. 

Lewis D. Mason, M.D., 

T. D. Crothers, M.D., 

Professor of Diseases of the Brain 
and Nervous System, the New York 
School of Clinical Medicine. 

Rev. Albert H. Plumb, D.D. 
William A. Mowry, Ph.D. 


Electrotyped tind Printed by 
J. B. Lippincott Company, Philadelphia , 17. S. A. 


ci* v 24 8 049 

SEP 13 >909 








PREFACE 


¥ 

This is the second book of a three-volume 
series of physiologies. The first book is only 
for children. The third book is adapted to 
the needs of the highest grades of the public 
schools, including high schools. This second 
book is graded to the needs and capacity of 
intermediate grades. 

Serious efforts have been made to present 
the various subjects in this book in a way that 
would make them plain and easy, and at the 
same time to teach some real physiology. A 
pupil may be interested and entertained with¬ 
out being instructed; but when interest is 
once aroused in the important facts of a sub¬ 
ject, instruction is sure to follow. 

The technical terms are used wherever 
needed. The names are not the difficult parts 
of a physiology. Technical styles of expression 
have been avoided, as they are not necessary 


IV 


PREFACE 


in a book of this character, and would only 
make an easy subject appear hard. 

A number of experiments have been incor¬ 
porated in the body of the text at points where 
they are most beneficial as an illustration. 
The live teacher will not omit a single one 
of these experiments, and will encourage the 
pupils to repeat the same and add others as 
far as possible. The experiments are an im¬ 
portant part of this grade of work. 

In regard to alcohol and narcotics, we have 
tried to present the truth as we see it, and as 
we have learned it from the research and ex¬ 
perience of others. A broad view should be 
taken of this subject. In the light of the ex¬ 
perience of the past, the nature of the sub¬ 
stance in relation to the cells of the body, and 
the investigations of modern times, there 
appears to be nothing to recommend the use 
of alcoholic drinks as a beverage The matter 
is thus presented in this series of physiologies. 

More cuts than are usually found in an in¬ 
termediate physiology are given in this book. 
Good cuts that illustrate the text are very 


PREFACE 


valuable in this stage of the pupil’s progress. 
A good text-book is always a little beyond the 
pupil, but the steps must be easy ones from 
what he knows to what he is striving to get. 
The cuts must be an aid in making these steps, 
or they may as well be left out. We have 
tried to have all the cuts in this book worthy 
of the space they take. 

We wish to acknowledge our obligation to 
the J. B. Lippincott Company for many cuts 
which appear in this book. 

Through the kindness of Ginn & Co. we 
were permitted to select two cuts from Blais- 
dell’s Physiology.’’ 







CONTENTS 

* 

CHAPTER PAGE 

I. Introductory.5 

II. Food ....... 20 

III. Digestion. 43 

IV. Care of the Digestive Organs . . 67 

V. Circulation of Blood . . . .79 

VI. Respiration ...... 109 

VII. The Skeleton ..... 142 

VIII. The Muscles. 167 

IX. The Skin. 187 

X. Excretion . . . . . .201 

XI. The Nervous System .... 209 

XII. The Special Senses .... 246 

XIII. Tuberculosis . . . . . .270 


vn 









ILLUSTRATIONS 


* 

FIG. PAGE 

1. A cell ....... io 

2. Cells of various kinds . . . . . n 

3. The amoeba ...... 13 

4. A shallow well . . . , . .27 

5. Glands ....... 45 

6. Section of teeth . . . . . -47 

7. A racemose gland . . . . .50 

8. Action of oesophagus . . . . .54 

9. Stomach and intestines . . . .56 

10. Section of small intestine .... 59 

11. A villus . . . .61 

12. Osmosis of liquids ..... 63 

13. The liver . . . . . .81 

14. The heart ....... 84 

15. Cavities of heart...... 86 

16. Action of valves ...... 86 

17. Valves of the heart ..... 88 

18. Branching of an artery .... 89 

19. Capillary V . . . . .91 

20. Valves in a vein ...... 92 

21. Red corpuscles ...... 94 

22. Microphotograph of red corpuscles . . 95 

ix 








ILLUSTRATIONS 


FIG. PAGE 

23. White blood-corpuscles .... 96 

24. Ciliated cells . . . . . .113 

25. The larynx ...... 115 

26. The vocal cords . . . . . .115 

27. Action of vocal cords . . . . .116 

28. Trachea . . . . . .117 

29. Bronchial tubes . . . . . .118 

30. The lungs . . . . . . .119 

31. Air-cells . . . . . .120 

32. Action of ribs . . . . . .121 

33. Exchanges in lungs . . . . .127 

34. Dust in air . . . • . .130 

35. Bacteria of consumption . . . .131 

36. Ventilation by window . . . 133 

37. The cranium ...... 144 

38. A vertebra . . . . .145 

39. The backbone . . . . 146 

40. The atlas on the axis . . . . .147 

41. Cartilage between vertebrae . . . .148 

42. The ribs ....... 149 

43. The pelvis . . . . . . 150 

44. The scapula . . . . . .150 

45. Bones of arm and hand . . . 152 

46. The carpus. . . ♦ . . .152 

47. Bones of leg and foot . . . . 153 

48. Hyoid bone . . . . . 154 

49. Bone tied in knot . . . . • 155 








ILLUSTRATIONS xi 

*IG. PAGE 

50. Section of femur . . . . .156 

51. Microscopic appearance of bone . . .158 

52. Hip-joint . . . . . . .162 

53. Ligaments of a shoulder-joint . . .164 

54. Action of a skeletal muscle . . . .168 

55. Muscle before and after contraction . .169 

56. Muscles and tendons of forearm . . .170 

57. The biceps. . . . . . .171 

58. Artery feeding muscle . . . . .173 

59. Muscles of the head and neck . . .175 

60. Fat tissue . . . . . . .180 

61. Section of skin . . . . . .188 

62. Cells of the epidermis . . . . .189 

63. Sweat-pores . . . . . .191 

64. The root of a hair . . . . .196 

65. Section of the end of finger . . .197 

66. Cell bathed in lymph ..... 202 

67. Section of kidney ..... 205 

68. A nerve-cell . . . . . .210 

69. Nerve-cells from brain . . . .212 

70. The human brain . . . . .214 

71. Convolutions of brain . . . . .215 

72. Section of nerve . . . . .217 

73. Section of spinal cord. . . . .218 

74. Piece of spinal cord . . . . .220 

75. Motor and sensory areas of cerebrum . . 224 

76. Relation of spinal nerves to cord . . .227 

w 






ILLUSTRATIONS 


xii 


FIG. 

77. Cell before and after fatigue . 



PAGE 

• 232 

78. Cross-section of eye 



248 

79. Muscles of the eye 



• 2 53 

80. Lachrymal gland 



• 2 55 

81. Pinna of ear 



• 258 

82. The three parts of the ear . 



• 2 59 

83. Tactile corpuscles 



. 262 

84. Indoor sleeping-tent—raised 



. 297 

85. Indoor sleeping-tent—in use 



. 298 






LIST OF EXPERIMENTS 


EXPERIMENT 

i. Action of saliva .... 



PAGE 

51 

2. Effect of mastication . 



52 

3. Swallowing .... 



55 

4. Action of oesophagus . 



55 

5. Action of pepsin 



58 

6. Passage of liquid through membrane 



64 

7. Veins in arm .... 



92 

8. Red corpuscles .... 



95 

9. The pulse ..... 



99 

10. Combustion .... 



hi 

11. Action of vocal cords • 



116 

12. Effect of exercise on breathing 



123 

13. Volume of air breathed 



124 

14. Air and candle-flame . 



I2 5 

15. Carbon dioxide .... 



128 

16. To tie a bone in knot . 



i 55 

17. To burn animal matter out of bone 



* 5 * 

18. To illustrate action of muscle 



168 

19. Perspiration from hand 



192 

20. Effect of draft of air on wet hand 



194 

21. Experiment with dry and wet thermometer 


194 


xiii 





xiv 


LIST OF EXPERIMENTS 


EXPERIMENT PAGE 

22. Determine direction of moving air . .194 

23. Effect of cornea and lens .... 249 

24. Action of pupil . . . . . .250 

25. Change of focus . . . . . .251 

26. To test sensitiveness of skin .... 264 

27. Location of touch . . . . .265 

28. Substance in solution before it can be tasted . 267 



SECOND BOOK OF PHYSIOLOGY 


CHAPTER I 

INTRODUCTORY 

Matter. —All substances and bodies that 
we know anything about are composed of 
matter. Anything that we can see or feel is 
matter. Water, rock, air, wood, bone, iron, 
gold, and so on, are all forms of matter. Our 
bodies are made of various kinds of material 
substances which we take into the body by 
eating, drinking, and breathing. 

Lifeless matter. —Lifeless matter is the 
kind that never moves or does anything of its 
own accord. Stones or wagons are lifeless 
because they will never move unless some 
outside force pushes or pulls them. The 
greater part of all the matter in the world is 
of this kind. The whole crust of the earth 


5 




6 SECOND BOOK OF PHYSIOLOGY 

and all the water and the air are lifeless mat¬ 
ter. The wind blows only when the sun makes 
it do so, and it, in turn, may raise waves on 
the water. 

A living body. —A living body is com¬ 
posed of matter, but the matter has been made 
over by a force called life . 

We can tell whether or not a body is alive, 
in three ways : (i) Within all live bodies there 
is motion. The heart beats, the breast rises 
and falls in breathing, and sap circulates in 
trees. (2) A live body can take up lifeless 
matter and make it part of its own body. All 
live bodies must have some kind of food. In 
that way they grow and get strong. A stone 
does not grow or do any work. (3) All live 
bodies can start the growth of other bodies 
just like themselves. An apple-tree produces 
seeds which will sprout and grow up into 
other apple-trees of the same kind. 

In short, then, all live bodies have motion 
within themselves , take in food , and produce 
other bodies of their own kind. 


INTRODUCTORY 


7 


Animals and vegetables. —All live bodies 
are either animals or vegetables. In some re¬ 
spects all live bodies are alike, but there are a 
number of plain differences between animals 
and vegetables. 

A vegetable is fixed to one place on the 
ground, while an animal can move about. 
A vegetable lives on a very simple kind of 
food which it gets from the ground through 
its roots, or from the air through its leaves, 
while an animal can live only on vegetables or 
other animals. Animals can feel and choose, 
while plants have no such power. 

Animals are a higher kind of living bodies 
than vegetables. 

Man’s place among living bodies.— 

Man is the highest of all animals. His body 
is not so large or so strong as that of some 
of the lower animals, but he has the best 
brain, and hence can know more than any other 
animal. A man can think, reason, invent, make 
plans, and prepare for the future. These things 
make man the master of all other animals. 


8 


SECOND BOOK OF PHYSIOLOGY 


Since this is so, we should think that all 
men would try to know all they can learn 
about their bodies and minds, and would be 
careful to observe the laws of good health. 

Many people do not take as good care of 

their health as some of the lower animals do. 

♦ 

Either they do not know any better or they 
are not willing to do what they should do. It 
makes no difference what the cause is, any 
one who does not obey the laws of health will 
have to suffer in some way. 

Purpose of this book. —The aim in this 
study is to learn all we can about the human 
body. When we know how nicely the differ¬ 
ent parts of the body are made and joined 
together, and how well all the parts work for 
the good of the whole body, we will certainly 
try in every way to help them, or at least 
will do nothing to hinder them. 

We will study this book, then, to find out 
the laws by which our bodies work, and then 
learn how to obey these laws so that we may 
have good health. 


INTRODUCTORY 


9 


Why we should study physiology.— 

The human body, in one sense, is a machine. 
No one should try to run a machine unless he 
knows something about it. 

If you were placed in charge of a printing- 
press, and were anxious to have it do the best 
kind of work for you for a long time, what 
would you do? No doubt you would care¬ 
fully examine it to see how it was put together 
and what work each part had to do. You 
would run it in such a way that it would do 
the best kind of printing for you. You would 
keep it clean, well oiled, and not allow any¬ 
thing to get into the cogs and break them. 
If any accident should happen to the press,, 
you would then know what to do. 

We study physiology for similar reasons, 
(i) To find out what the different parts of the 
body are. (2) To find out the use of each 
part. (3) To find out how to take proper 
care of the body. 

The body composed of cells. —The 

body is made up of many millions of very 


IO SECOND BOOK OF PHYSIOLOGY 

small bodies called cells. The cells are so 
small that they can be seen only with a good 
microscope. The flesh, the bone, the skin, 
the hair, and so on, are all made up of a great 
number of these little cells. In Fig. i the 



Fig. i.—A cell, a , cell-wall; b , albumin ; c, nucleus. 

parts of a cell are shown. Within the cell, 
at some point, is always a nucleus. Around 
the nucleus is the albumin. Outside of all is 
the cell-wall. The nucleus is the centre of the 
life of the cell, and without it the cell would 
soon die. The albumin is a substance about 
like the white of an egg. It makes up the 
larger part of the cell. The cell-wall forms a 
little chamber, or cell, in which the nucleus and 
albumin are placed. In most vegetables this 
wall is thick and strong, but in animals it is 
-often very thin or entirely wanting. 



INTRODUCTORY 


Forms of cells. —When a great number 
of cells are joined together to form a body 




Fig. 2.—Cells of various kinds. /, plant cells ; s , pavement cells; t, 
columnar cells ; w , ciliated cells; m y muscle-cells ; tt y nerve-cells. 


like that of a tree, a horse, or a man, the cells 
press against each other and are made to have 

































12 


SECOND BOOK OF PHYSIOLOGY 


many different shapes. Also, the different 
kinds of cells have different kinds of work to 
do, and they are made so they can do their 
work in the best way. In Fig. 2 you can see 
the shapes of several kinds. The upper one 
shows some cells arranged in the tip of a root 
of a plant, s shows a few flat cells joined 
edge to edge like stones in a pavement, i 
shows a few cells standing on end like columns. 
The cells shown in w have cilia, or hair-like pro¬ 
jections on top. Two different kinds of muscle- 
cells are seen at m , and two nerve-cells at n. 
There are a number of other cells of different 
shape, each being adapted to the kind of work 
it has to do. 

Single - celled animals. — There are a 
great number of very small animals which are 
composed of but a single cell. They are, in 
most cases, so small that they can be seen only 
with very strong microscopes. 

A very good example of this kind of animal 
is shown in Fig. 3. It is called the amoeba . 
It lives in water and moist earth. If you 


INTRODUCTORY 


3 


could see one of them it would look like a 
very small lump of jelly with a round dot in¬ 
side. If you would continue to watch it, you 
would see that it is alive, for it would begin to 



Fig. 3.—The amoeba. 


move in a very peculiar way. It has no feet, 
but instead it pushes out one side of its body 
in the direction it wishes to go and then rolls 
the rest of the body into it. In that way it 
moves along, and when it rests it is in the 
shape of a tiny ball. 

It has no stomach or mouth, but when it 
meets any small particles of food it wraps its 
whole body around it and takes the food into 
its body. In that way it can make a stomach 
for itself whenever it needs one. 

The amoeba lives much as other animals do ; 
but its life is very simple, for it has only one 
cell, and must use it for everything it does. 



14 


SECOND BOOK OF PHYSIOLOGY 


The human body made of cells.— A 

great number of cells much like the amoeba are 
found in the human body. They float about 
in the blood and move through other parts of 
the body. They are called white corpuscles, 
and will be described in a later chapter. 

The most of the cells of our bodies do not 
move about. The muscles, bones, skin, brain, 
liver, and so on, are all made up of many cells ; 
but they are fixed to one spot and their food 
is brought to them by the blood. 

One cell cannot do very much, but when a 
great number of them work together to do the 
same thing they can do a great deal. One boy 
cannot pull a heavy wagon along the road, but 
when a number of boys all pull and push in 
the same direction, the wagon can be moved 
along rapidly. 

A division of work among the cells of 
the body. —In a large factory of any kind the 
work is divided among the men who are at 
work there. If they are making shoes, one set 
of men will prepare the leather; another will 


INTRODUCTORY 


*5 


cut it out; another will sew the pieces to¬ 
gether, and so on till the shoe is complete. 
They can make shoes much better that way 
than if each man tried to do all the different 
kinds of work. 

The human body is like this factory, and the 
different sets of men at work are like the dif¬ 
ferent groups of cells in the human body. 

Each group of cells has become used to one 
kind of work and does not try to do any other 
kind. The cells in the stomach look after the 
digestion of food. Those of the skin work 
for the protection of the outside of the body. 
Those in the muscles move the body. Those 
in the heart keep the blood in motion. Those 
in the brain reach out long arms to the other 
cells and control their action. A great num¬ 
ber of groups of this kind are engaged in 
doing a special kind of work, and each can do 
better work than if it tried to do many dif¬ 
ferent things as the amoeba has to do. 

An organ. —An organ of the body is com¬ 
posed of a large number of cells which work 


16 SECOND BOOK OF PHYSIOLOGY 

together to do a certain thing. The stomach 
is an organ of digestion. The lungs are the 
organ of breathing. The eye is the organ 
of sight. The ear is the organ of hearing. 
Whenever we use the word organ in this book, 
it will mean a collection of cells which are all 
working together to do some important work 
for the body. 

The different kinds of matter in the 
body. —The whole body is made up of water , 
albumin , fat , minerals , and a little sugar. 
About three-fourths of the whole body is 
water. Even the cells of the hard bone and 
teeth are partly water. 

The albumin is a very important part of all 
the cells. In a good-sized man there are about 
twenty pounds of it. 

About ten pounds of a man’s weight is fat, 
sometimes more and sometimes less than that 
amount. 

Minerals are found in all parts of the body, 
but mostly in the lime in the bones. Salt 
is a mineral found in all the cells. 


INTRODUCTORY 


J 7 


How the body is kept alive. —The body 
is a machine, and, like all machines, it must be 
kept going or it will stop. Food and air are 
the two things which we take into the body, 
and they keep the cells alive and make them 
able to do work. 

What does the engineer do when he wants 
his engine to run ? He shovels good coal into 
the fire-box under the boiler, and opens the 
damper so the fire can get a good draft of fresh 
air. The coal is the food of the engine and the 
draft of air is its breath. As long as the coal 
and air are supplied, the engine can be kept 
running; but as soon as either fails, the fire 
goes out and the engine stops. The engine 
may then be said to be dead, but a fire may 
be started in it at any time, and it is then alive 
again. 

Eating and breathing are the two most im¬ 
portant things we have to do. The food and 
the air do for us what the coal and air did for 
the engine. We have to eat about three times 
a day, and must breathe constantly both day 
and night. If we could not get food and air 


jg SECOND BOOK OF PHYSIOLOGY 

the body would soon die, and, unlike the en¬ 
gine, life could not be started in it again. 

QUESTIONS. 

1. What is matter ? 

2. What is lifeless matter ? Give some examples. 

3. In what three ways does a live body differ from 
lifeless matter ? 

4. What are the two kinds of live bodies ? 

5. Give three important differences between animals 
and plants. 

6. Give some good reasons for studying physiology. 

7. What three things should we find out by this 
study ? 

8. What are the three parts of a cell? 

9. Draw on paper or the blackboard several cells of 
different shape. 

10. Describe the amoeba. How does it walk and eat ? 

11. What is the human body composed of ? 

12. How is work divided among the workmen in a 
large factory ? 

13. How is work divided among the cells of the body ? 

14. What advantage is there in having different groups 
of cells for each special kind of work ? 

15. What is meant by an organ of the body ? 

16. What five substances are in the human body? 


INTRODUCTORY 


*9 


17. How much of the whole body is water? 

18. How much of the body is albumin? 

19. How does an engineer keep his engine going? 

20. How do we keep the body alive and able to do 
work ? 


CHAPTER II 


FOOD 

What food does for the body. —Food 
does three things for the body. (i) It adds to 
the weight of the body. A growing boy or 
girl needs a great deal of food for this pur¬ 
pose. When they are full grown their weight 
will change very little during health. (2) The 
food unites with the oxygen of the air which 
we breathe and produces heat. A healthy 
body has almost exactly the same temperature 
all the time. (3) Food stores all the cells with 
material which they can use in doing work. 
In walking, running, and working the muscles 
are active and use up the material which the 
food brought to them. 

In short, then, warmth, growth, and ability 
to do work are the three things which we get 
from food. 

Why we have to continue to eat.— 

Some one might say that he eats because he 


20 


FOOD 


21 


is hungry, but that would not be correct. We 
get hungry only when we need more food. 
We have to keep on eating because the food 
is rapidly used up and the body is constantly 
wearing away. Every breath which is breathed 
out from the lungs carries heat and water out 
of the body. On a cold day, even when we 
are well clothed, a great deal of heat gets 
away from the body. The body gets its heat 
only by burning up some of the food which 
we eat, and so that is one reason why we get 
hungry. 

The chief purpose of food is to furnish 
energy, that is, ability to do work. 

When a man works hard he soon gets hun¬ 
gry, and needs to eat more than one who is 
idle. This is because the food which is stored 
in blood and in the cells of the body is rapidly 
used in doing work. Then the man eats again 
and uses that food in doing more work. 

The skin is constantly wearing off and new 
cells from beneath form new skin. 

In other ways, too, the body is constantly 
losing material, so that, in all these different 


22 


SECOND BOOK OF PHYSIOLOGY 


ways, the body of a man who is doing hard 
work will lose about nine pounds a day. This 
must be supplied by the food which the man 
takes into his body. 

What a food is. —A food is anything that 
will nourish the body without doing it harm. 
Bread, milk, meat, eggs, and many vege¬ 
tables are good foods because they supply 
the cells of the body with what they need. 
Alcohol is not a food, because, even if it does 
make the body warmer for a time, it also 
injures the cells. 

Difference between the food of plants 
and animals. —The chief difference between 
a plant and an animal is in the kind of food 
which they use. 

All animals live on plants, and plants live 
on the food which they get from the soil and 
the air. All plants are at work making food 
for animals. If plants should cease to grow, 
all animals would starve for want of food. 
When we eat beefsteak we eat the food which 


FOOD 


2 3 


the ox got from the plants. The food in an 
egg was obtained by the hen from the plants. 
All of our food was prepared first by vege¬ 
tables. 

Different kinds of food. —There are three 
important kinds of food. They are proteid y 
starch , and fat. 

The proteids are the most important of all. 
The larger part of a living cell is proteid, and, 
as it is constantly being used up, the food 
must bring it a new supply. The white of an 
egg is almost all proteid. Proteid is found 
only in the live cells of animals and vegetables. 

Starch is also an important food which is 
prepared for us by the vegetables. Wheat, 
corn, oats, potatoes, and many other vege¬ 
tables contain a large quantity of starch. The 
starch itself is not a food to the cells ; but the 
body has an easy way of changing it to sugar, 
as we will explain in the next chapter, and the 
cells then use the sugar. 

The fats are obtained chiefly from fat meats, 
butter, milk, oils, and nuts. Fat is food which 


24 


SECOND BOOK OF PHYSIOLOGY 


is stored up in the body. It may not be needed 
just at present, but it is always ready for use. 
When an animal cannot get food, it will live a 
long time on its fat, and then it will be very 
lean. 

There are two other substances which we 
must have, and they may properly be classed 
as foods, though they are used in a different 
way from the three great foods named above. 
These two are minerals and zvater. 

The minerals are needed to build up the 
parts of the body that do not change very 
much. Bone is hard and strong because it 
contains a great deal of lime. All the ma¬ 
terial from which bone is made must come 
from the food which we eat. 

Salt is another important mineral which is 
needed by all the cells. There is some salt 
in our food, and we add a great deal more in 
cooking or at the table while we are eating. 
Other minerals are also needed, but they are 
already in the other foods. 

Water is not used up in the body as the 
proteids, starches, and fats are, but it is always 


FOOD 


2 5 


needed to dissolve the other foods and to float 
them out to the cells. A cell can neither work 
nor get its food unless it is bathed in water. 
The impurities which are made in the body 
must be washed away, and this is always done 
by the water. A man can live many days 
without the other foods, but he would hardly 
get through a single day without water. 

Good water. —A man needs about three 
quarts of water every day. Part of this is 
taken with other foods, such as milk and vege¬ 
tables ; but he must drink a great deal besides. 

There is little danger that any one will ever 
drink too much pure water. Most people 
drink too little. The great danger lies in 
drinking water that is not pure. 

Water may be very clear and yet be very 
impure. The little germs of disease which 
live in water are so small that they cannot be 
seen with the naked eye. Water may be 
muddy, and yet be purer than some clear 
water. A filter may make the water clear, but 
it will not always make it pure. When water 


26 SECOND BOOK OF PHYSIOLOGY 

has a foul smell it is not fit to drink; but im¬ 
pure water cannot always be detected by the 
smell of it. How then can we tell whether the 
water which we drink is pure or not ? It is 
not always an easy matter. A bottle of the 
water may be sent to a chemist once in a 
while, and he can analyze it and see if it con¬ 
tains any impurities; but most people cannot 
go to that trouble and expense. The best 
way is to avoid water found in places where it 
is likely to be impure. The water in shallow 
wells, stagnant pools, and rivers into which the 
sewage of a city is emptied, is never safe to 
drink. 

Shallow wells. —When it rains, the water 
either soaks into the soil or runs into the low 
places, forming the lakes and rivers. The part 
that soaks into the ground will run through 
cracks in the rock or through openings of any 
kind in the ground. In that way numerous 
veins of water are formed in the earth, some 
close to the surface and some deep in the 
rock. There are so many of these veins that 


FOOD 


27 


when we drill or dig into the earth we are 
almost sure to strike one of them and get a 
well of water. When a well is drilled deep 
into the rock and cased up with iron tubes, the 



Yig. 4.— The kind of wells that are liable to contain impure water. 


water in it is almost always pure and good to 
drink. This is so because the water has soaked 
through layers of sand, gravel, and clay, and 
then passed back and forth in the crevices of 
the rocks down to the bottom of the deep 



28 


SECOND BOOK OF PHYSIOLOGY 


well. This is nature’s way of filtering water 
and making it pure. 

Impure well-water is nearly always found in 
shallow wells. This is what we would expect. 
The rain-water gathers up many impurities, 
decaying matter, and disease germs and car¬ 
ries them into shallow wells. Such wells are 
often twenty, thirty, or forty feet deep, and 
are walled up with stone. Foul water can run 
through the wall into the well. The platform 
upon the well and the sod around it may be 
kept very neat and clean, but still the water 
may become very foul. Filth from a barnyard, 
outhouse, or sewer may be carried into such 
a well by a vein of water under the ground. 
Typhoid fever and other diseases are often 
caused by drinking water from such wells. 

Shallow wells are always likely to contain 
foul water, and should be avoided if possible. 
Such wells in a city or town are much more 
dangerous than in the country. 

City water. —Many cities and towns are 
supplied with good water from wells and 


FOOD 


29 


springs or lakes. Such water is often brought 
from a long distance and pumped through 
pipes into the city. One of the most im¬ 
portant things a city or town has to do is to 
supply its people with good drinking-water. 
City water sometimes also becomes impure 
and many people become sick, for everybody 
must drink water. When it is suspected that 
water contains germs which cause disease the 
only safe course is to first boil the water for 
twenty minutes or more. This will kill all 
living germs. 

Freezing the water will not purify it. It is 
a bad practice to put broken ice into the drink¬ 
ing-water. The ice may be impure, and it 
makes the water too cold for a healthful 
drink. 

Some good foods. —Wheat is one of our 
best foods because it contains all the different 
kinds of foods we have named. It is rich in 
proteid and starch, and also contains some 
sugar and fat. Dough made of flour is sticky 
because of the gluten in it, and gluten is chiefly 


3° 


SECOND BOOK OF PHYSIOLOGY 


a proteid food. When yeast is mixed with it, 
the whole lump of dough will “rise.” This is 
caused by millions of little yeast-plants which 
grow rapidly in dough. They set free a great 
number of bubbles of gas called carbon diox¬ 
ide. The sticky gluten holds the bubbles in 
the dough, and as the amount of gas increases 
the dough is forced to “ rise.” When the 
dough is placed in a hot oven it will rise rap¬ 
idly, because the heat makes the gas expand. 
Baked bread will contain numerous holes where 
the gas was formed. 

One can live very well on good bread and 
butter alone. 

Corn is rich in starch and fats, but has only 
about one-half as much proteid as wheat has. 
That is why corn bread will not rise as well 
as wheat bread. Corn bread is a wholesome 
food. 

Peas, beans, potatoes, and many fresh veg¬ 
etables are also desirable foods when mixed 
with other foods. 

Meats and eggs are rich in proteid and fat. 
They are valuable foods for men who do hard 


FOOD 


3 1 

work, but not so good for boys and girls or 
for those who sit at their work all day. Meats 
should always be well cooked. Beefsteak is 
much better than pork. 

Good milk is a perfect food for children, 
but it alone is not enough for people who 
are grown. 

The need of a mixed diet. —While bread 
contains all the different kinds of foods, it is 
not best to eat bread alone. We would have 
to eat too much starch to get the right amount 
of proteid. It is better to eat some good 
meat or egg with the bread. In that way we 
can get just the right amount of each kind. 
Fresh vegetables and fruits are also necessary 
to a good diet. 

Amount of food. —While there are some 
who do not have enough to eat, yet probably 
more sickness and disease are caused by eat¬ 
ing too much rather than by eating too little. 
One should quit eating as soon as he begins 
to feel satisfied. It does not require much 


3 2 


SECOND BOOK OF PHYSIOLOGY 


good food to keep the body strong and in good 
health. Too much food only creates poisons 
in the body. 

Cooking. —Most foods should be cooked. 
The starch in wheat, rice, corn, potatoes, and 
other foods are much more easily digested 
when cooked. All food must be in a liquid 
form before it can get into the blood. Starch 
when cooked is readily changed to sugar. 

Meats should be cooked to make them 
tender. They can then be finely ground 
between the teeth and will be more rapidly 
digested in the stomach. 

Cooking also makes the meat taste better, 
and if it should be diseased, as often happens 
in pork, the heat of cooking will prevent any 
harmful effect. Pork should always be cooked 
through and through. 

Good cooking is as necessary to good 
health as good food. 

A good cook in a family is of greater ser¬ 
vice than a doctor. 

There are many excellent cook-books from 


FOOD 


33 


which any girl who desires may learn to be a 
good cook. 

Alcoholic drinks. —Water and milk are 
drinks which are furnished by nature. Natural 
drinks are the only ones ever needed, but man 
has manufactured a number of drinks, such as 
wine, cider, beer, and whiskey. These all con¬ 
tain alcohol, and their use as drinks has done so 
much harm in the world that every one should 
know something of their source and nature. 

Source of alcohol. —Alcohol is produced 
by a process called fermentation. Fermenta¬ 
tion is caused by very minute round plants 
called yeast germs. These little plants may 
be found on the skins of fruit and floating in 
the air in almost every place. They thrive 
and rapidly increase in number whenever they 
can get food and warmth. When placed in 
sweet liquids, like the expressed juices of 
fruits, they change the sugar into two other 
substances, one, a gas called carbon dioxide, 
and the other alcohol. The carbon dioxide 


3 


34 SECOND BOOK OF PHYSIOLOGY 

bubbles up through the liquid and escapes, 
but the alcohol remains in the liquid. 

The purpose of fermentation. —Fermen¬ 
tation is the first step in decay. Plants get all 
their food from the ground and the air, and 
they build up complex substances, such as 
starch, sugar, and proteids, which are the food 
of animals. But the ground and the air would 
soon be impoverished if plants were constantly 
taking something from them and never return¬ 
ing anything to them. So, whenever a plant 
or an animal dies, there are numerous little 
germs of various kinds which will, unless pre¬ 
vented, break up the complex substances into 
simpler ones. These simple substances are 
then free to return to the air and the ground 
and be used again in the growth of plants. 

In case of fruits, grains, and some other 
substances, the first step in the process of 
decay is fermentation. The carbon dioxide 
returns to the air, and the alcohol is soon 
changed to other substances suitable for plant 
food. Right here is where man steps in and 


FOOD 


35 


stops the process of nature. He collects the 
alcohol and uses it as a drink. Nature never 
prepares an alcoholic drink. Nature does 
prepare grain and ripe fruit, and seems to 
hold these out to us as our proper food, but 
alcoholic drinks are prepared by men inter¬ 
fering with nature. 

Nature of alcohol. —It is the nature of 
alcohol to injure the health of the body and, 
when taken in sufficient quantity, to produce 
death. Alcohol is, therefore, a poison. 

It is also the nature of alcohol to benumb 
the senses and produce stupor. For this 
reason alcohol is classed as a narcotic poison. 

Cider. —Cider is made of the juice of apples. 
When apples ripen, the starch which they con¬ 
tain is changed to sugar and so the juice is 
sweet. Such juice is healthful. It is a natural 
food. On the outside oi the apple, however, 
are a number of the yeast germs ready to 
change the healthful juice in the manner we 
have just described. 


36 SECOND BOOK OF PHYSIOLOGY 

When the juice is pressed out of the apples, 
the yeast germs at once begin their work, and 
in about six hours alcohol may be found in the 
cider. They continue their work until the 
cider becomes “hard,” when it may be one- 
tenth alcohol. 

Cider, as it is usually prepared, is an alco¬ 
holic drink. Its use will injure the health of 
the body and, as has often been the case, may 
set up an appetite for stronger and stronger 
drink. 

Wine. —Wine is made from the juice of 
grapes. Ripe grapes are a healthful food. 
When the juice of grapes is pressed out, the 
yeast germs from their surfaces mingle with it 
and fermentation at once begins. Thus the 
healthful grape juice is changed to an alcoholic 
drink called wine. Grape juice is a product 
of nature, but wine is a product of decay. 

Wine is one of the worst of drinks, because 
it has the power to create a strong appetite 
for more and more wine or leads to the use 
of much stronger drinks. 


FOOD 


37 

In those countries and states where wine¬ 
making is the chief industry, the people are 
poor and degraded. If, instead of destroying 
this natural food, they would dry the grapes 
and use them or sell them as raisins, they 
would enrich their country by this profitable 
industry and relieve themselves from the evil 
effects of wine-drinking. 

Beer.—Beer is made from grain. Grain 
contains a large proportion of starch which 
nature can readily change to sugar, and then 
the yeast germ can begin the process of fer¬ 
mentation. When wheat-flour, for example, 
is made into a dough and mixed with yeast, 
the yeast changes the sugar in the flour to 
alcohol and carbon dioxide. The bread will 
“rise” for reasons explained on page 30. 
When the dough is placed in the oven, the 
heat will cause a rapid evaporation of any 
alcohol present. Well-baked bread does not 
contain any alcohol. 

Beer is made by first sprouting the grain to 
change the starch to sugar. Then this grain 


38 SECOND BOOK OF PHYSIOLOGY 

is boiled along with hops and some other sub¬ 
stances which are added to flavor the beer. 
To this solution is then added the yeast which 
causes the liquid to ferment. The result of 
the fermentation is the usual carbon dioxide 
and alcohol. 

Thus, while bread contains only the health¬ 
ful product of nature, beer contains these sub¬ 
stances after they have begun to decay, and 
includes the poisonous alcohol which nature 
never would have saved up if man had not 
checked her process. 

Strong drinks.—Any alcoholic drink may 
be made into stronger drinks by separating 
some of the water from them so they may 
contain a larger per cent, of alcohol. This 
is done by a process called distillation. The 
liquid containing the alcohol is heated in a still. 
The alcohol boils and is changed to a vapor 
first. This vapor passes off through a long 
coil, where it is cooled and condensed to a 
liquid again. Most of the water is left behind 
and that which passes over is rich in alcohol. 


FOOD 


39 


Whiskey, brandy, rum, and other such strong 
drinks are made in this way. 

Alcohol as a food.—Some people drink 
beer, whiskey, and other drinks that contain 
alcohol. They say that it keeps them warm 
in winter-time and makes them strong and 
healthy. This is a great mistake, as we will 
show in several places in this book. Alcohol 
is a poison to the cells of the body. It will 
make the body warmer for a while, but it also 
causes the body to lose much more heat 
than it gains from the alcohol, as will be 
shown in the chapter on the circulation of 
the blood. 

There is nothing in alcohol to build up the 
body. The only way it could be a food would 
be in making heat, and in that it does more 
harm than good. 

Some people think certain kinds of alcoholic 
drinks, such as beer, are good food because 
they make people fat. But fat people often 
have very poor health and can do very little 
work. Beer will make people fat, but it at 


40 


SECOND BOOK OF PHYSIOLOGY 


the same time will make them unhealthy. It 
makes fat cells take the place of cells in the 
muscle, liver, kidney, and so on. In that way 
those organs are made weaker instead of 
stronger. Fat cells are of no use in the oper¬ 
ation of the body. Beer, then, cannot be a 
food, because it destroys good cells and puts 
poor ones in their place. 

The worst results from the use of alcohol 
are its poisonous effects on the cells. A little 
alcohol may seem to do no harm, and the 
body can recover from its effects as it does 
from sickness. But any alcohol in a healthy 
body will do harm. Continued drinking of 
beer, whiskey, brandy, hard cider, and other 
such drinks is sure to result in a weakened 
condition of some of the important organs of 
the body. 

A food will supply what the body needs, 
without doing harm, and so alcohol cannot be 
classed as a food. 

A healthy appetite will call for the proper 
kind of foods, and it never calls for alcohol. 

An appetite for strong drink is always 


FOOD 


4i 


caused by a diseased condition of the body 
brought on by alcohol itself. 

Tea and coffee.—Tea and coffee are not 
foods. They belong to a class of substances 
called stimulants. They may stimulate the 
organs of the body to greater activity, but do 
not furnish any of the energy needed to do the 
extra work. They hinder rather than help 
digestion. 

The practice of tea-drinking is especially 
bad where the teapot is kept “ stewing” at 
all times and a “ sup” of tea is taken at short 
intervals. When one learns to rely on this 
kind of stimulant, it is difficult to do without 
it, and its evil effects increase with every drink. 

Both tea and coffee are particularly harmful 
to children and young people during their 
period of growth. 

QUESTIONS. 

1. What are three uses of food ? 

2. Define a food. 

3. How does our food differ from that of plants? 

4. Name three kinds of food. 


42 


SECOND BOOK OF PHYSIOLOGY 


5. What is proteid? 

6. Whence do we get the starches? 

7. What is the use of fat ? 

8. What is the use of the minerals ? 

9. Explain why the water in a shallow well is liable 
to be impure. 

10. What is the source of water that you drink? 

11. Why is wheat a good food ? 

12. What causes bread to rise ? 

13. Why not eat only bread ? 

14. How-much should one eat? 

15. Why should starch be cooked ? 

16. Give some reasons for cooking meat. 

17. How is alcohol produced ? 

18. What is the use of fermentation ? 

19. What is the nature of alcohol ? 

20. How does the juice in an apple differ from hard 
cider ? 

21. Describe wine-making. 

22. How is beer made ? 

23. How does beer differ from bread ? 

24. How are strong drinks made ? 

25. Does alcohol make the body warm ? 

26. Does alcohol make the body fat ? How ? 

27. Is alcohol a food ? Why not? 

28. What evil effect from drinking tea and coffee ? 


CHAPTER III 


DIGESTION 

The use of digestion.—The organs of 
digestion, all taken together, form a long tube 
of uneven size. At some places the tube is 
small and at other places it swells out into a 
pouch like the stomach. This tube is a pas¬ 
sage-way for the food from the mouth clear 
through the body. 

While food is in the tube it is still on the 
outside of the body. Food is not properly in 
the body until it is in the blood. It must get 
through the walls of the tube to the numerous 
small blood-vessels on the other side. This 
cannot be done until the food is first changed 
to a liquid form. Much of it must also be 
changed into other kinds of substances. 
Starch, for example, must all be changed to 
sugar, and the sugar is then easily dissolved. 
Then it is carried through the walls of the 
tube and joins the current of blood. 


43 


44 


SECOND BOOK OF PHYSIOLOGY 


The organs of digestion.—Most of the 
food must pass through several changes before 
it is fully digested. These changes are made 
at different points along the tube. One kind 
in the mouth, another kind in the stomach, still 
another in the intestines, and so on. We shall 
describe the several different organs of diges¬ 
tion in order,—the mouth, pharynx , oesophagus , 
stomach , small intestine , and large intestine. 

Mucous membrane.—The whole digest¬ 
ive tube is lined with mucous membrane. 
This is, in fact, a kind of skin which lines all 
cavities in the body that open in any way to 
the outside. It can be seen in the mouth and 
nostrils. It lines the whole mouth and ex¬ 
tends on down along the gullet and covers 
the inside of the stomach. Extending on, it 
lines the whole intestines. At the lips it can 
be seen how the hard outer skin joins to 
the soft mucous membrane. 

The mucous membrane is very important 
in digestion. It is made of cells which have 
different shapes in different places. Some of 


DIGESTION 


45 


these cells pour out upon the surface of the 
membrane a sticky fluid called mucus. This 
is what makes the saliva “ropy.” Other cells 
are busy collecting juices of one kind or 
another and pouring them upon the food as 
it passes along. 




Fig. 5. —Glands. A, mucous membrane ; B, fold forming gland; 
C, compound gland. 


A gland.—The mucous membrane in 
places will fold in and line a pocket as shown 
















46 SECOND BOOK OF PHYSIOLOGY 


in B, Fig. 5. The cells in such a pocket, or 
pouch, undertake a special duty of collecting 
liquids from the blood and making them over 
so that they can do some special work. For 
example, several groups of cells arranged in 
this way will produce saliva and pour it into 
the mouth. Others will produce gastric juice 
and pour it into the stomach. Other juices 
used in digestion are produced in a similar 
way. Such a group of cells is called a gland. 
Often a number of these pockets are joined 
together in one gland as shown in Fig. 5, C. 
The liquid gathered by the gland is poured 
out through a tube called a duct. 

Digestion in the mouth.--The first work 
of digestion is accomplished in the mouth. 
Here two things should take place. (1) The 
food should be ground into very fine pieces 
by the teeth. (2) It should be thoroughly 
mixed with saliva. Both are important oper¬ 
ations in digestion. 

Teeth.—The teeth begin to cut through 
the gums when a child is only about six 


DIGESTION 


47 


months old. They keep coming, one after 
another, until he is about two years old. 
Then he has ten teeth in each jaw. These 
are only temporary teeth. They do not last 


A B 



Fig. 6.—Section of teeth. A , molar; B, incisor. 


long. At the age of five or six years another 
set begins to grow just beneath the temporary 
ones. The new teeth gradually push the old 
ones out. At the age of twelve or thirteen the 
new set, called the permanent teeth, have all 
appeared. Of these there are fourteen in each 
jaw. At the age of twenty or twenty-five 
years the “wisdom teeth” appear, making 
the full set of sixteen in each jaw. 




48 SECOND BOOK OF PHYSIOLOGY 


Kinds of teeth. —There are four kinds of 
teeth in each jaw. (i) The incisors (the 
cutters). There are four of these in each jaw 
in front. They have a sharp edge and are 
fitted to bite off morsels of food. (2) The 
canines (dog teeth). There are two of these 
in each jaw, one on each side just back of the 
incisors. (3) Biscupids (two cusps), two on 
each side, just back of the canines. (4) 
Molars (grinders), the three large back teeth 
on each side. 

The structure of teeth. —The part of a 
tooth which extends beyond the gum is called 
the crown. The part fastened into the bone of 
the jaw is the root. The front teeth have but 
one root, and the back ones have two or more. 
All are firmly fixed into the bone with cement. 

The crown is covered with a very hard sub¬ 
stance called enamel. Enamel is the hardest 
substance in the body. It needs to be hard, 
so that the teeth will not be worn away by the 
constant biting and grinding which they have 
to do. 


DIGESTION 


49 


On the inside of a tooth is a cavity which is 
filled with a soft substance called pulp . In 
the pulp are numerous small blood-vessels 
and nerves. Around the pulp is a hard bony 
material called dentine , and outside of all is 
the enamel. The blood-vessels bring the 
needed food to the cells in the hard substance 
of the tooth, and the nerves notify the mind 
whenever anything goes wrong in the tooth. 
Teeth will easily decay when they do not 
receive proper care. 

Use of teeth. —Good teeth that are kept 
in good condition will add a great deal to 
one’s personal appearance, but their chief 
use is to grind the food. This grinding is the 
first act of digestion, and it is an important 
one. 

When you wish anything to dissolve rapidly 
in water you first pound it into a fine powder 
and then stir it into the water. In the same 
way the food must be ground into fine bits so 
that it can be easily and rapidly changed by 
the digestive juices. 



5o 


SECOND BOOK OF PHYSIOLOGY 


Saliva. —Saliva is a thin watery fluid which 
is collected by six glands located about the 
lower jaw. One gland is located just below 
and in front of each ear, and the other four are 
beneath the tongue. They 
are known as the salivary 
glands. They are composed 
of a great many sacs, or 
pockets, all joined together 
so that the whole has the ap- 
FlG 7 ^d aCem ° Se P earance °f a bunch of grapes, * 
as shown in Fig. 7. 

Just outside the pockets of the gland are 
numerous fine blood-vessels. As the blood 
passes along, the cells in the gland take up 
the liquid which they make into saliva. 

Use of saliva. —While the food is being 
ground by the teeth, the salivary glands are 
busy making saliva and pouring it into the 
mouth through their ducts. The saliva has 
two important uses. (1) It moistens the food 
so that it can be ground still finer by the 
teeth and can be easily swallowed. Dry food 



DIGESTION 


5i 


would stick in the throat. (2) It dissolves 
part of the food. Such substances as candy, 
sugar, and salt are dissolved in the mouth by 
the saliva. There is also in saliva a ferment 
which changes some of the starch into sugar, 
and the sugar is then dissolved. Not much 
af the starch is changed to sugar in the mouth; 
but after the food is swallowed and gets down 
into the intestines, the ferment of the saliva 
continues to change starch to sugar. 

It is important that food be finely ground 
and well mixed with saliva before it is swal¬ 
lowed. 

Experiment 1.— Cook a little starch and 
make of it a thin paste. Fill a small bottle or 
test-tube about half full of the starch paste 
and add to it a little saliva, about a table- 
spoonful. Shake the bottle and keep it at 
about the temperature of the blood in the 
body, 98° Fah. The starch paste had a cloudy 
appearance, but after the saliva was added it 
soon cleared up. The starch was changed 
to sugar and then dissolved in the water of 


5 2 


SECOND BOOK OF PHYSIOLOGY 


the mixture. The liquid now has a sweet 
taste. 

Experiment 2. —Put into a glass of water 
some chunks of hard candy. Into another glass, 
containing the same amount of water, put the 
same amount of candy, but first pound it till 
it is broken into fine grains. Stir the liquid 
in both glasses, and notice how much sooner 
the candy in the second glass will dissolve. 
The same can be done with ice or rock-salt. 

This will illustrate the advantage of chewing 
the food into fine bits. 

The pharynx. —Just back of the mouth 
is an irregular cavity, or box, called the 
pharynx. The pharynx has seven open¬ 
ings. Two at the top lead into the nostrils. 
One at each side opens to the ears. One in 
the bottom leads to the stomach and another 
to the lungs. In the front, the pharynx opens 
into the mouth. 

After the food has been chewed and mixed 
with the saliva, it is pushed by the tongue 
into the pharynx. Then all the openings are 


DIGESTION 


53 


closed except the one which leads to the 
stomach, and the food is thus started down 
the tube called the oesophagus. Close by the 
oesophagus is the windpipe, but there is a lid 
on the top of the windpipe and it closes down 
whenever we swallow. The food then slides 
over the top of this lid to the opening of the 
oesophagus which is just behind. Sometimes 
particles of food get under the lid and into the 
windpipe, causing violent coughing. 

The two parts of the trunk of the body. 

—Before we describe digestion further, we 
should here learn that the trunk of the body 
is divided into two parts by a partition called 
the diaphragm . The diaphragm stretches 
clear across the cavity of the trunk and is 
fastened to the walls of the trunk near the 
lowest pair of ribs. 

The part of the trunk above the diaphragm 
is called the chest or thorax. The thorax con¬ 
tains the heart, lungs, and large blood-vessels. 

The part below the diaphragm is called the 
abdomen. It contains the stomach, intestines, 


54 


SECOND BOOK OF PHYSIOLOGY 


liver, kidneys, spleen, pancreas, and many 
small blood-vessels. 

The oesophagus. —The oesophagus is a 
tube which runs from the pharynx down 



Fig. 8.—(Esophagus. 

through the thorax and through the diaphragm 
into the stomach. All digestion is done in the 
mouth and in the abdomen. Food passes 
rapidly from the mouth to the stomach. 

One layer of muscle in the wall of the 
oesophagus runs around the tube. When a 



DIGESTION 


55 


lump of food enters the top of the tube, a 
ring of muscle will contract just above it and 
make the tube smaller on that side. In that 
way the food is pushed down a little way. 
Then other rings contract in the same way 
and push the lump of food farther and farther 
until it reaches the stomach. 

It is not possible to swallow unless there is 
something in the oesophagus. When food is 
once started down the oesophagus, it will be 
carried on to the stomach without any further 
attention. 

Experiment 3.—Swallow two or three 
times to remove the saliva from the mouth. 
Then try to swallow again. You probably 
will not succeed. If you do, try two or three 
more times rapidly, and you will find at last 
that, however hard you may try, you cannot 
perform the act of swallowing. This is be¬ 
cause there is nothing to swallow. 

Experiment 4.—Secure a piece of soft 
rubber tubing and fill it with putty or soft 


56 SECOND BOOK OF PHYSIOLOGY 

clay. Hold it as shown in Fig. 8 and close 
one finger after another against the tube. By 



doing so the putty will be pushed out at the 
lower end of the tube. This illustrates how 
the oesophagus pushes the food down to the 
stomach. 

The stomach. —We have said that the 
food is all digested in a long tube which runs 




DIGESTION 


57 


from the mouth through the body. We have 
now traced some food from the mouth to the 
pharynx, and then into the oesophagus, which 
carried it down through the thorax and dia¬ 
phragm. We have now come to a place 
where the tube widens out into a large pouch 
called the stomach. 

The stomach is placed in the upper part of 
the abdomen and on the left side. It presses 
against the lower side of the diaphragm. The 
food enters the stomach at the cardiac orifice 
and leaves it at the pyloric orifice. (See 
Fig- 9 -) 

The mucous membrane which lines the 
stomach contains numerous small glands. 
These produce gastric juice and pour it out 
freely upon the food in the stomach. The 
gastric juice contains acid and is quite sour. 
It rapidly digests all proteid foods. That is, 
substances like white of egg, meat, gluten of 
bread, and so on. It does not change the 
starch or the fat. 

A layer of muscle in the walls of the stom¬ 
ach will contract on one side, and then on the 


58 SECOND BOOK OF PHYSIOLOGY 

other, thus keeping the food in motion and 
mixing it with the gastric juice. 

All the proteids, fats, starches, and other 
foods are mixed together, making a mass 
something like thick cream. This mass is 
called chyme. 

In a short time after a meal, some of the 
food has been digested. The pyloric orifice 
opens and lets this part out. Little by little 
the chyme flows out, and in from two to four 
hours.the stomach should be empty again. 

Experiment 5. —Secure at a drug-store a 
small bottle of pepsin in a solid form. Put 
about one teaspoonful of it into a half-teacup 
of warm water. Stir till it dissolves. Add 
four or five drops of hydrochloric acid. This 
will be a gastric juice. 

Thoroughly mince a very little of the white 
of a hard-boiled egg and place it in the cup. 
Keep it warm, about 98° Fah. In an hour 
or less the egg will be dissolved. The action 
is better observed if a bottle or test-tube is 
used instead of the cup. 


DIGESTION 


59 


This will illustrate the kind of digestion 
which takes place in the stomach. 

The small intestine. —When the chyme 
leaves the stomach it enters the small intestine. 



Fig. io.—S ection of small intestine. 


This is a tube about twenty feet in length. 
It begins at the stomach and is folded from 
side to side in the lower part of the abdomen, 
and finally opens into the large intestine. 

As soon as the chyme from the stomach 
enters the small intestine, it is mixed with two 
fresh juices which were prepared for its com¬ 
ing. These are the pancreatic juice and the 


6o 


SECOND BOOK OF PHYSIOLOGY 


bile. The work of digestion was begun in the 
mouth and continued in the stomach, and 
these new juices now complete the digestion. 

Pancreatic juice. —The pancreatic juice 
rapidly changes all starch to sugar, and 
changes the fats so they can get through 
the mucous coat of the intestines. 

This juice is collected by a racemose gland 
called the pancreas. The pancreas is a slender 
body about eight inches long, and lies just 
back of the stomach. The special work of its 
cells is to produce pancreatic juice whenever 
it is needed, and pour it out through a duct 
upon the food in the small intestine. 

The bile. —The liver is a large and very 
important gland, which will be described a 
little farther on in this book. It has many 
duties to perform, and one of them is to col¬ 
lect bile , which is poured upon the food along 
with the pancreatic juice. 

Bile is a yellowish fluid, which is collected 
in the gall-bladder under the liver and emp¬ 
tied upon the food when needed. 


DIGESTION 


61 


It gives valuable help to the pancreatic 
juice in completing the process of digestion. 

The chyle. —After the food is fully di¬ 
gested in the small intestine it is called chyle. 
Chyle is a thin white liquid. The fat is not 
dissolved, but only broken up into very fine 
particles which make the chyle look white. 



The food is now all digested and ready to 
enter the blood ; but how does it get to the 
blood-vessels ? 

The villi. —The inner surface of the small 
intestine is thickly covered with small projec- 


















62 SECOND BOOK OF PHYSIOLOGY 

tions which look a little like the nap on a 
piece of velvet. These are the villi , which 
dip into the liquid food. In Fig. io is a section 
across the small intestine of a cat. The sec¬ 
tion is very thin, and so the villi do not seem 
to be crowded, but they stand close together 
all over the surface. 

When a single villus is closely examined 
with a microscope, it is seen to be covered 
with a layer of cells, as shown in Fig. 11. On 
the inside are numerous fine tubes, which run 
in every direction and are connected together 
so as to form a fine net-work. These are 
blood-tubes, and because they are so small 
they are called capillaries. Another tube of 
a little different kind runs up through the 
villus. It is called a lacteal , because after 
digestion it is filled with a milky-white liquid. 

How the food gets into the blood. —We 

see, then, that there is only a very thin layer 
of cells between the food in the intestine and 
the tubes in the villi. The blood is flowing 
through the capillaries in the villi all the time, 


DIGESTION 


63 


whether there is any food to be taken up or 
not. But when there is rich food in the intes¬ 
tine, and the blood needs it, some is sure to 
soak through the layer of cells and join the 



Fig. 12.—Apparatus to illustrate the passage of liquids through a 
membrane. 


stream of blood as it flows along. The albu¬ 
min, and sugar, and water, and minerals go 
into the blood capillaries, but the fine globules 
of fat go into the lacteals. That is what makes 
the lacteals white. 












64 SECOND BOOK OF PHYSIOLOGY 


Experiment 6.—Strip some of the outer 
membrane from a large piece of bologna and 
tie it tightly over the bottom of a lamp chim¬ 
ney. Fill the chimney to a depth of an inch 
or two with a solution of strong salt water, 
and support the chimney so that the bot¬ 
tom dips into fresh water, which is slightly 
colored with some aniline dye. In an hour 
or more the fresh water will have a salty taste, 
and some of it, as shown by the color, will 
have passed up into the chimney. This shows 
how liquid foods may easily pass through a 
similar membrane to the capillaries. 


QUESTIONS. 

1. When is food properly in the body ? 

2. Why is digestion necessary ? 

3. Name the parts of the tube through which the 
food passes during digestion. 

4. Describe the mucous membrane. 

5. What is a gland, and how are they formed? 

6. What is the duct of a gland? 

7. What are the first two acts of digestion ? 

8. Describe the temporary set of teeth. 

9. Describe the permanent set of teeth. 


DIGESTION 


65 


10. Name and locate the different kinds of teeth. 

11. What is enamel ? 

12. What is on the inside of a tooth? 

13. What important work of digestion do the teeth 
have to perform ? 

14. How is saliva made ? 

15. What are two uses of saliva? 

16. Describe and perform an experiment showing how 
saliva acts on starch. 

17. Describe an experiment showing that food should 
be broken into fine bits. Perform the experiment. 

18. Where is the pharynx ? 

19. What are the seven openings from the pharynx ? 

20. How does food get across the top of the windpipe 
without falling in ? 

21. What is the diaphragm ? Where is it ? 

22. What organs are in the thorax ? 

23. What organs are in the abdomen ? 

24. Where is the oesophagus ? 

25. How does the oesophagus push the food down to 
the stomach ? 

26. Describe and perform an experiment showing how 
the oesophagus works. 

27. Where is the stomach? 

28. What are the two openings of the stomach ? 

29. How is gastric juice made ? 

30. What kind of food will gastric juice digest ? 


5 


66 


SECOND BOOK OF PHYSIOLOGY 


31. What is chyme ? 

32. How long does food remain in the stomach? 

33. What kind of food will pancreatic juice digest? 

34. How is pancreatic juice made ? 

35. How is bile made ? 

36. Describe the small intestine. 

37. What is chyle ? 

38. What is the use of the villi ? 

39. Describe a villus. 

40. How does the food get from the intestines into 
the blood? 


CHAPTER IV 


CARE OF THE DIGESTIVE ORGANS 

Advantage of healthy organs of diges¬ 
tion. —All of our strength comes from the 
food which we eat. We have to eat every 
day to get ability to work. This is true not 
only of work which we do with our muscles, 
but we cannot think well unless we eat and 
digest good food. 

The only natural way by which food can 
get into the blood is through the organs of 
digestion. It is very necessary that these 
organs be kept in a healthy condition, for we 
must rely upon them for our supply of food. 

An unhealthy condition of the stomach or 
intestines not only makes a man very miser¬ 
able, but also weakens all the other parts of 
the body by cutting off their supply of food. 

A healthy stomach is a great blessing. 
With proper care it will always do its work 

67 


68 SECOND BOOK OF PHYSIOLOGY 

very faithfully, but it may easily be disordered 
by improper usage. 

Dyspepsia is a common disorder of the 
stomach, which is usually caused by bad foods 
and improper eating. 

The best time to take good care of the 
stomach is while it is in a healthy condi¬ 
tion. 

Chewing the food. —It is important that 
the food be thoroughly chewed before it is 
swallowed. Good cooking and proper prep¬ 
aration of foods are a great help in digestion; 
but still the food should be kept in the mouth 
long enough to grind it very finely and mix it 
with saliva. It is a bad habit to take water or 
other drinks into the mouth to hurry dry food 
down the throat. Bread and other dry food 
should be moistened in the mouth only by 
saliva. 

Care of the teeth. —It will not be possible 
to grind the food thoroughly unless there is a 
good set of molars. The permanent set of 


CARE OF THE DIGESTIVE ORGANS 69 

teeth may be kept sound for a long time, but 
without proper care they will soon decay. 

Decay begins in a small spot on a tooth, 
and, if allowed to continue, will widen and 
deepen till it reaches the pulp and produces a 
violent ache. 

Teeth should be examined by a dentist 
once or twice a year, and any decay can thus 
be checked at the beginning and the tooth 
can be saved. 

Teeth should always be cleansed after eat¬ 
ing. Decay may be started by small particles 
of food which become wedged in between the 
teeth. These particles should be removed 
after each meal by use of a soft wooden tooth¬ 
pick, and the teeth should be brushed with 
some good tooth-wash or some mild soap. 

Teeth that are neglected often become cov¬ 
ered with a coating called tartar. This makes 
the teeth yellow and gives the whole mouth a 
repulsive appearance. It can be removed by 
a dentist, and the teeth may afterwards be kept 
clean and white by frequent washing with a 
stiff brush. 


7 o 


SECOND BOOK OF PHYSIOLOGY 


When decayed teeth cannot be repaired, 
they should at once be removed from the 
mouth. 

Care of the stomach. —If the stomach 
is kept in a healthy condition, all the other 
organs of digestion will be cared for at the 
same time. But when the stomach fails to 
do its work, the whole body suffers at once. 

Nearly all the ills of the stomach result 
from improper methods of eating, poor food, 
good food poorly prepared, and taking inju¬ 
rious substances which are not foods into the 
stomach. 

Eating too much or too often is a common 
evil. The stomach, like other organs, needs 
periods of rest. The best cure for indigestion 
is, often, to eat nothing for a time. 

Eating too rapidly will throw undue work 
upon the stomach, for the food will not be finely 
chewed, and so must remain a longer time in 
the gastric juice before it will be digested. 

Food that is not properly cooked is often 
a cause of much of the trouble in digestion. 


CARE OF THE DIGESTIVE ORGANS 71 

There is a way of preparing even the simple 
foods, such as bread, potatoes, and meats, so 
that they not only taste much better, but can 
be more thoroughly digested. 

Mental condition has much to do with diges¬ 
tion and a healthy stomach. 

A gloomy state of mind has a depressing 
effect on every organ of the body. A cheerful 
and happy state of mind will assist digestion. 
The conversation at the table should be, if 
possible, only on pleasing topics, and all 
worry should be cast aside. 

A short period of rest and relaxation before 
and after meals is a great aid to digestion. 
This is true of both mental and physical labor. 
Any part of the body that is being hard 
worked will take a larger amount of attention 
and blood than usual. For this reason, hard 
study or intense physical exercise will, to some 
extent, decrease the activity of the digestive 
organs. 

Effect of alcohol on the organs of 
digestion. —Alcohol hinders digestion and 


72 


SECOND BOOK OF PHYSIOLOGY 


produces a diseased condition of the digestive 
organs. 

It was once quite common to have wines, 
beer, whiskey, or other alcoholic drinks 
served at meals. It was believed that they 
were a food, and also that they helped to 
digest other foods. Careful study has shown 
that this is a grave mistake, and those who 
care for their health no longer use alcoholic 
drinks in this way. 

Alcohol makes food less digestible. Pro- 
teid, in particular, is hardened and shrivelled 
by alcohol, and must remain longer in the 
stomach before it is digested. 

If alcohol acted on the food only, its bad 
effect would not be so great. But it injures 
the linings of the stomach itself. 

Most drinkers are troubled with catarrh of 
the stomach. The delicate mucous mem¬ 
brane becomes inflamed and sore. The gas¬ 
tric glands are thus weakened and diseased. 
They cannot produce gastric juice of the right 
quantity or quality. 

Thus alcohol makes the food less digestible, 


CARE OF THE DIGESTIVE ORGANS 73 


and at the same time weakens the organs of 
digestion. 

When the stomach is not healthy, it causes 
a great deal of suffering and misery. If, at 
such times, a drink containing a large amount 
of alcohol be taken, the pain may, for a time, 
cease. The drinker is often deceived by this, 
and thinks the alcohol is making him well 
because it stopped the pain. The truth is. 
that the alcohol only made the trouble still 
worse ; but it did benumb the ends of the 
nerves so that there was no pain for a while. 
As soon as the effect of the alcohol is gone, 
the pain is likely to be greater than before. 

Moderate drinking. —When alcohol is 
taken in large amounts, its poisonous effect 
can be very plainly seen. But when it is 
drunk in small amounts, and only now and 
then, it may appear to have no bad effect. 
The body is able to recover from the injury 
done by the alcohol when the amount is small. 
This is true of any poison. A few very small 
doses of arsenic may be thrown off by the 


M SECOND BOOK OF PHYSIOLOGY 

body, and none of the cells may suffer any 
particular injury, though arsenic is a strong 
poison. 

Alcohol is also a poison to the cells of the 
body, no matter whether the amount is large 
or small. The reason a small amount does 
not at once plainly poison the body is because 
the body is strong enough to fight it off or to 
recover from slight injuries. 

Bread, meat, and other foods will supply 
the cells with what they need, but alcohol 
always tends to do them harm. 

Appetite for strong drink. —Nearly all 
drunkards began by drinking just a little now 
and then. A little is enough to start an ap¬ 
petite for more. The appetite grows until 
only a large quantity will satisfy it. 

A healthy appetite is a good thing. It is 
the body’s way of telling us when it needs 
food. When the body is perfectly healthy, it 
is safe to eat and drink whatever the appetite 
calls for. But many people do not have an 
appetite that they can safely follow. They 


CARE OF THE DIGESTIVE ORGANS 75 

have acquired appetites that will lead them to 
take harmful substances into the body. 

It is easy to cultivate an appetite for things 
that will injure the body, and that is why it is 
often an unsafe guide. 

An appetite is easily created for alcohol, 
tobacco, opium, and a number of drugs. 
Each time it is gratified it grows stronger, 
and after a while it cannot be refused. 

This is another reason why moderate drink¬ 
ing is a bad practice, for, little by little, it 
creates an appetite for more. In this way 
many have become drunkards. 

Amount of alcohol in some common 
drinks. —The common drinks that contain 
alcohol are malt liquors , wine , and strong 
drinks. 

Malt liquors are such as beer and ale. The 
strongest of them do not contain more than 
one-tenth alcohol. These liquors are made 
from grain. 

Light wines, also, are about one-tenth al¬ 
cohol, but a great deal of alcohol is often 


76 SECOND BOOK OF PHYSIOLOGY 

added to wines. Sometimes one-third of the 
wine is alcohol. 

Strong drinks are those that contain a large 
amount of alcohol. They are such as whiskey, 
rum, and brandy, all of which are about one- 
half alcohol. 

Patent medicines. —Some of the patent 
medicines contain more alcohol than is ever 
found in beer or wine. These medicines are 
sold at every drug-store and are widely ad¬ 
vertised as cures for a great many ills. Some 
of the most widely known of these medicines 
are from one-fifth to nearly one-half alcohol. 
The bitters which are offered as cures for 
stomach trouble contain a large quantity of 
alcohol, and give relief of the same kind that 
a glass of whiskey gives. 

Tobacco and digestion. —Tobacco com 
tains a substance called nicotine , which in a 
pure state is very poisonous. Those who 
use tobacco are almost sure to get some of 
this poison into the stomach. When one is 


CARE OF THE DIGESTIVE ORGANS 77 

not used to tobacco, it will make him very 
sick. This shows that it is something which 
does harm, or the organs of digestion would 
not rebel against it. A full-grown man 
whose body has become used to tobacco may 
not appear to be harmed by smoking a cigar 
once in a while, but the effect of tobacco, like 
alcohol, is always something from which the 
body has to recover. 

The constant use of tobacco has a bad 
effect on the mucous membrane of the mouth 
and throat and stomach. 

The sense of taste becomes dull, and the 
appetite is often destroyed. 

Those who are still growing are always 
harmed by the use of tobacco in any form. 

QUESTIONS. 

1. Give some advantages of a healthy stomach. 

2. What is dyspepsia? (See dictionary.) 

3. Why should water not be taken into the mouth 
with the food ? 

4. Give several rules for the care of the teeth. 

5. What is the effect of eating too much ? 

6. How will eating too rapidly injure the stomach ? 


7 8 


SECOND BOOK OF PHYSIOLOGY 


7. How can cooking assist the stomach ? 

8 . How does worry affect digestion ? 

9. Why should one have rest before and after meals ? 

io. What effect does alcohol have on the stomach? 
n. Why does alcohol seem to help a disordered 

stomach ? 

12. Does a little alcohol do harm? 

13. What is the use of appetite? 

14. How may an appetite be spoiled ? 

15. Name several drinks and tell how much alcohol 
they contain. 

16. What are malt liquors? (See dictionary). 

17. How much alcohol in patent medicines ? 

18. What are some of the bad effects of tobacco? 


CHAPTER V 


CIRCULATION OF BLOOD 

Why the blood must circulate. —The 

blood receives all the food and every cell of 
the body needs food. But the cells are nearly 
all fixed in one place and cannot go after their 
food, so it must be brought to them. The 
muscles in the arm, for example, would soon 
become weak and helpless if fresh food were 
not constantly brought to them in the stream 
of blood. The cells in the brain would at 
once cease their action if the supply of blood 
were shut off. We would not be able to think, 
if the brain-cells did not get a constant supply 
of blood. 

When a cell uses its food, it always pro¬ 
duces some waste matter that must be carried 
away. The circulating blood does this also. 

Circulation, then, does two important things 
for the body: (i) It carries food to the cells. 
(2) It carries waste matter away from them. 

79 


So SECOND BOOK OF PHYSIOLOGY 

How the stream of blood gets a fresh 
supply of food. —The stream of blood is 
forced by the heart to go around and around 
through every part of the body. At one place 
in its circuit it comes very close to the food in 
the intestines. Here is where the blood takes 
up a fresh supply of food. 

The blood may be compared to a delivery- 
wagon which makes a circuit through a city 
and delivers groceries from house to house. 
Each time the wagon completes a circuit it is 
again loaded at the grocery and proceeds with 
its work of distribution. 

The blood flows slowly through the fine 
tubes in the villi of the intestines at all times, 
and some food is taken into it at all times, but 
most rapidly just after the digestion of a hearty 
meal. 

All the food, except the fats, as soon as it 
gets into the current of blood, is carried 
straight to the liver. 

The liver. —The liver is one of the organs 
of digestion because it makes the bile which 


CIRCULATION OF BLOOD 81 

is needed in digestion. But it has other work 
to do which is more important than making 
bile. 

The liver is a gland. It is the largest gland 
in the body. It is placed on the right side 



of the body just below the diaphragm, and 
weighs from three to four pounds. It is made 
up of a great number of liver-cells, and be¬ 
tween the cells are thousands of fine tubes, 
which carry blood through the liver close 
to the cells. These cells make important 
changes in the blood while it flows by them. 

6 


82 SECOND BOOK OF PHYSIOLOGY 

The use of the liver. —All the blood that 
circulates through the walls of the stomach 
and intestines, where the new food is taken 
up, is next carried to the liver. The liquid 
food is not ready to go to the heart until it is 
first acted on by the liver. 

The sugar that was eaten, and the starch 
that was turned to sugar, are stored up in the 
liver. In that way this large gland acts as a 
storehouse for the body, and deals out food 
little by little as we need it. If it were not 
for this work of the liver, we would have to 
eat a little nearly all the time, just as we now 
have to breathe all the time because we have 
no storehouse for air. 

The liver also takes out of the blood many 
things which would harm or poison the cells 
if allowed to circulate through the body. In 
that way the liver is always on guard and 
always trying to keep the blood pure. 

The liver, then, does three things : (i) It 
makes bile for use in digestion. (2) It acts 
as a storehouse of food. (3) It purifies the 
blood. 


CIRCULATION OF BLOOD 83 

After the food passed through the liver it 
was carried by a large vein up to the heart. 

The thoracic duct. —Nearly all the food 
that was taken up from the intestines was car¬ 
ried by blood-vessels straight to the liver. But 
most of the fat did not go that way. We saw 
in Fig. 11 that each villus contains, besides 
the fine blood-vessels, another tube called a 
lacteal. These tubes gather up the fat and 
carry it to the thoracic duct. The thoracic 
duct is a tube which runs along the spinal 
column and joins a large vein in the left 
shoulder. In this way the fats are also carried 
to the heart. 

The course of the blood. —The blood is 
forced by the heart to go out through tubes 
that run to every part of the body and then 
return to the heart again. These tubes are 
all closed so that the blood cannot get out, 
except as some parts of it may soak through 
to the cells. The organs that make the blood 
circulate and carry it through the body are the 
heart , arteries , capillaries , and veins. 


84 


SECOND BOOK OF PHYSIOLOGY 


The heart. —The heart is the chief organ 
of circulation. The blood would soon cease 
to flow if the heart should quit beating. The 



Fig. 14.—Human heart. I, right auricle ; 2, right ventricle; 3, pul¬ 
monary artery ; 4, left auricle ; 5, left ventricle ; 6, aorta. 


heart is just above the diaphragm at about the 
centre of the chest. It is a hollow bundle of 
muscle in the shape of a pear. Its large end 


CIRCULATION OF BLOOD 85 

is towards the right shoulder, and the small 
end points forward and to the left. 

The heart is enclosed in a bag called the 
pericardium. This bag is lined with a very 
smooth membrane, which is always moist. 
When the heart beats, there is almost no fric¬ 
tion between it and the pericardium. 

The heart is double. —The heart is a 
double organ. There are two separate hearts 
joined together as one. They are called the 
right heart and the left heart. The right 
heart receives all the blood as it returns from 
its journey through the body and sends it to 
the lungs. The left heart receives the blood 
when it comes back from the lungs and sends 
it out through all parts of the body. The left 
heart has much the harder work to do, and so 
it is stronger. 

The cavities of the heart. —Each side of 
the heart contains two cavities. The upper 
ones are called auricles and the lower ones 
ventricles. So there is a right auricle and a 


86 SECOND BOOK OF PHYSIOLOGY 

right ventricle , and a left auricle and a left ven¬ 
tricle. These parts are shown in Fig. 15. 
Each auricle is separated from its ventricle by 
a valve. 



Fig. 15.—Four cavities of the heart. R A, right auricle ; R V y right 
ventricle ; L A, left auricle ; L V\ left ventricle. 

How valves work.—Valves are in com¬ 
mon use in pumps and in many machines 



which we use every day. By the use of two 
valves, a liquid can be made to flow always in 










CIRCULATION OF BLOOD 87 

the same direction. In Fig. 16, B is a strong 
rubber bulb ; o and x are valves. If B is now 
filled with water and then squeezed with the 
hand, the water will start to flow out at both 
ends. But this will close x and open o, and 
all the water will flow towards s. If the hand 
be now opened, the walls of the bulb will 
spring back and start to draw water in at both 
ends. But this will close o and open x. The 
water will then be drawn only from W. If 
the bulb be now squeezed again, this water, 
also, will be sent towards 

Valves of the heart.—The valves in the 
heart are arranged in about the way we have 
just described. The blood flows into the 
heart, and then the strong muscular walls 
squeeze upon it and force it out. But this 
would be of no use if the blood could flow 
back through the same tubes by which it 
entered ; so each side of the heart is pro¬ 
vided with two valves. The right heart has 
two and the left two. These valves are 
shown in Fig. 17. The blood enters first 


88 SECOND BOOK OF PHYSIOLOGY 

into the right auricle, D , and flows through the 
valve, e , called the tricuspid valve. This valve 
opens only towards the right ventricle. When 
the muscles of the right ventricle contract, the 



valve, e , will be pushed shut, and the blood can 
get out only through the valve, m, called the 
semilunar valves , which open only outward. 
In that way the blood is pushed through the 
tube, kS, which carries the blood on to the lungs. 

When the blood returns from the lungs it 
enters the left auricle, K\ and passes on 





CIRCULATION OF BLOOD • 89 

through the valve, i, called the mitral valve , 
into the left ventricle, H. When the left ven¬ 
tricle squeezes upon the blood, the valve, z, is 
pushed shut and n opens. Thus the blood is 
forced out through A and carried all through 
the body. 

Arteries.—Arteries are tubes which carry 
blood that is sent out from the heart. They 



Fig. 18.—Branching of an artery. 


are elastic, like a rubber tube, and always 
stand open whether there is any blood in 
them or not. 





9° 


SECOND BOOK OF PHYSIOLOGY 


One large artery leads out from each ven¬ 
tricle. The one from the right ventricle is 
called the pulmonary artery because it carries 
the blood to the lungs. The one from the 
left ventricle is called the aorta . It is the 
large tube that curves up over the heart, as 
shown in Fig. 14. 

The aorta sends off branches to the head, 
arms, legs, trunk, and, in fact, to every part 
of the body. These branches divide into finer 
and finer branches until at last the artery is 
so small it cannot be seen without a micro¬ 
scope. Some of the fine branches are shown 
in Fig. 18, but a line cannot be made on paper 
as fine as the smallest arteries. 

Capillaries—The capillaries are tubes still 
finer than the finest arteries. When the blood 
reaches the end of an artery, it passes into the 
capillaries. The plan of the capillaries is 
shown in Fig. 19. All arteries carry blood 
into capillaries, and all capillaries pass the 
blood on into veins. 

It is while the blood is slowly 


movinor 

o 


CIRCULATION OF BLOOD 91 

through the capillaries, that the food oozes 
through to the cells. 

All parts of the body are filled with capil¬ 
laries. It is not possible to push a fine needle 



through the skin without piercing one or more 
of these fine blood-tubes and letting out some 
blood. They are very small, varying in length 
from to tsW of an inch. 

The whole use of the heart and the arteries 
is to keep the capillaries filled with blood. 

Veins.—Blood moves through capillaries 
at the rate of about one inch in a minute. 
This gives time for the liquid food in the blood 
to get to the cells, and for the waste in the 
cells to get into the blood. 

The blood is then collected by a vein. 
Veins are at first very small ; but a great num- 



9 2 


SECOND BOOK OF PHYSIOLOGY 


ber of them unite and form larger and larger 
ones, just as many small streams of water 
often unite to form a large river. All veins 
are at work carrying blood back to the heart 
after it has passed through 
capillaries. 

Veins do not have thick 
walls, like arteries, but they 
have many valves, while ar¬ 
teries have none. These 
valves are only small pock¬ 
ets on the inside of the 
fig. 20.—Valves in a vein. vein. When the blood 
flows towards the heart the 
valves do not hinder it, for they are pushed 
up against the side of the vein. But if the 
blood starts to flow in the other direction, the 
pockets fill up and close the vein. 

Experiment 7. —Bare the arm and notice 
the numerous blood-vessels just under the 
skin. These are all veins. They are carry¬ 
ing blood up the arm towards the heart. Grasp 
the arm tightly and notice that the veins will 





CIRCULATION OF BLOOD 


93 


soon become swollen with blood on the side 
next to the hand. Notice also that knots 
appear here and there along the veins. These 
are caused by the valves. 

All the smaller veins from the parts of the 
body below the heart are joined to one very 
large vein which carries the blood up to the 
heart. A short piece of it can be seen in 
Fig. 17, b. All the veins from the head, arms, 
and other parts above the heart unite in one 
large vein which carries the blood down to 
the heart. (Fig. 17, c.) 

Blood.—Blood is a liquid which the heart 
forces around and around through the arteries, 
capillaries, and veins. The blood has three 
important duties to perform : (1) To take up 

the food after it is digested, and distribute it 
to the cells in all parts of the body (2) To 
take up oxygen which we breathe into the 
lungs, and carry it to the cells. (3) To gather 
up waste matter and carry it to the lungs, 
kidneys, or skin, where it is cast out. 

The blood is made up of a thin liquid in 


94 


SECOND BOOK OF PHYSIOLOGY 


which a great number of corpuscles are always 
floating. These corpuscles are of two kinds, 
the red and the white. 

Red corpuscles.—Fresh blood is always 
a bright red, but the color is all due to the red 
corpuscles. These little bodies 
are so numerous that they 
make all the blood look red. 

(Q S (?) The red corpuscles are very 

small discs of solid matter. 
They have the shape shown in 

Fig. 21.—Red blood- y-. T u . i 

corpuscles. Fl g- 21 ■ lt WOuld take OVer 

10,000 of them, placed one 
upon the other, to make a pile one inch high. 

These little discs are a very important part 
of the blood. They are the oxygen carriers. 
Every time they pass through the lungs each 
one takes up a small load of oxygen and car¬ 
ries it out to the capillaries, where the oxygen 
is given up to the cells. 

While the corpuscle is loaded with oxygen 
it is a bright red color, but after it has passed 
through the capillaries and lost the oxygen, it 








CIRCULATION OF BLOOD 


95 


is no longer red, but purple in color. So the 
blood in the arteries is red, and in the veins, 
purple. The only exception to this is that 
the artery from the right ventricle to the lungs 
carries purple blood, while the vein from the 
lungs to left auricle carries red blood. 

Experiment 8.—Pierce the skin of the 
thumb with a fine needle, and let out a small 



Fig. 22.—Microphotograph of red corpuscles. 


drop of blood. Smear it upon a clean slip of 
glass so that it is spread out very thin. Then 
place the glass under a compound microscope 
and look for red corpuscles. They will not 
appear very red unless a great number of 


96 SECOND BOOK OF PHYSIOLOGY 

them are seen together. Fig. 22 is a photo¬ 
graph of human blood as seen through a 
strong microscope. The blood on the spot 
that was photographed was so thin it could 
scarcely be seen with the naked eye. 

White corpuscles. —White corpuscles are 
found floating in the blood with the red ones. 


They are larger than the 
but there are not 
ly so many of them. 
j are single cells and 
a nucleus. Their 

_ements and manner 

of life are very much like 
that of the amoeba. A 



Fig. 23.—White blood- 
corpuscles. 


white corpuscle may rest and float along in the 
blood, or it may slowly move itself about. 
When it wishes, it can stretch itself into a fine 
thread and can go right through the wall of 
a blood-vessel into other parts of the body. 

The use of the white corpuscle. —The 

white corpuscles are of great service to the 
body. They are all the time in search of any 


CIRCULATION OF BLOOD 


97 


small particles that would do the body harm, 
and, if they can, they will permit nothing to 
be in the blood or muscles, or other parts of 
the body, unless it rightly belongs there. 
When one cuts his finger, it may become very 
sore. This is because there are always many 
little live germs in the air and on the skin, 
which get into the cut. They find good food 
there, and will multiply and live there unless 
they are destroyed. When this happens, the 
white corpuscles will gather around them in 
such numbers that the wound will become 
swollen and inflamed. They attack the little 
enemies that do not belong in the body and 
try to destroy them. In most cases they will 
succeed and the enemy will be driven out, but 
many of the white corpuscles lose their lives 
in the conflict, and the white matter, called 
pus, which appears in the sore, is composed 
of their dead bodies. 

So we may think of the white corpuscles 
as a kind of standing army within the body. 
When the health is good, the standing army 
will be strong and can easily repel any enemies 

7 


98 SECOND BOOK OF PHYSIOLOGY 

that try to get in. When the health is bad 
and the body weak, one can more easily catch 
a disease because his standing army is 
weak. 

Blood-clot. —The body has many ways of 
keeping itself well, fighting off disease, and 
healing up wounds. The doctor could do 
very little for the body if it did not do a great 
deal for itself. 

A slight cut would soon let out all the 
blood, and life would cease, if there were no 
way to stop it; but nature has a way of check¬ 
ing its flow by forming a blood-clot in the 
wound. While in the blood-vessels the blood 
is thin, but as soon as it is outside it becomes 
quite thick. It would be very difficult to stop 
bleeding at the nose if a blood-clot did not 
stop the end of the fine artery from which the 
blood comes into the nose. 

When a large artery is cut, the blood comes 
out so fast that the clot cannot stop it, and the 
surgeon must be called to tie the end of the 
artery. 


CIRCULATION OF BLOOD 


99 


The pulse. —The pulse beats as often as 
the heart does. It can be felt at any place 
where an artery, of good size, runs close to the 
surface. It can be most easily felt and counted 
at the wrist, just a little above the thumb. 

The arteries are full of blood all the time, 
and every time the left ventricle contracts it 
forces more blood into the aorta. This causes 
a pulse, or wave, to run out through all the 
branches of the aorta. This is what we can 
feel at the wrist. 

Experiment 9. —Break or cut off a piece 
of mirror about as large as a penny, or smaller. 
Fasten it to the wrist with a piece of chewing 
gum, at the point where the pulse can be most 
plainly felt. Now stand at a window and hold 
the mirror so that the sunlight, falling upon it, 
will be reflected to the ceiling of the room. 
The arm must be held still, and the pulse will 
tilt the mirror so as to make the bright spot 
on the ceiling move through a distance of one 
foot or more. 

Change in the size of arteries.— The 

walls of the arteries are provided with mus- 


ioo SECOND BOOK OF PHYSIOLOGY 

cles which run around the arteries. When 
these contract, they make the tube smaller and 
less blood can get through. When they relax, 
the tube gets larger and more blood flows. 
This is all regulated by nerves which are con¬ 
nected to these muscles. When any part of 
the body needs more blood, the arteries that 
carry blood to that point will open and let more 
flow. When one goes out on a cold day, the 
small arteries under the skin will contract and 
keep the blood in nearer the centre of the body. 
This keeps the heat from escaping too fast. 

Different paths of the blood in its cir¬ 
cuit. —When blood is forced out by the heart 
through the aorta, it goes to all the capillaries 
in the body. But the part that goes to the 
stomach and intestines, where the fresh food is 
taken up, is gathered up by a large vein, called 
the portal vein , and carried to the liver. In the 
liver this blood is changed and purified, as has 
already been explained, and then carried up 
by a large vein to the heart. 

Another branch from the aorta carries blood 


CIRCULATION OF BLOOD 


IOI 


to the kidneys. There the poisonous urea 
and a large amount of water are taken out. 
This blood, too, is then emptied into the large 
vein that leads up to the heart. 

The large artery from the right ventricle car¬ 
ries the blood to the lungs, where water and 
carbon dioxide are taken out of it, and oxygen 
is taken up by the red corpuscles. 

While this is going on, other portions of the 
blood are out in the muscles, the bones, the 
skin, and every part of the body, feeding the 
cells. So the blood is flowing through many 
different circuits at the same time. 

Beating of the heart. —If the hand be 
placed on the left side, at a point between the 
fifth and sixth ribs, the beating of the heart 
may be distinctly felt. The two sides of the 
heart work together. Both auricles contract 
at the same time and fill the ventricles. Then 
the two ventricles contract,—the right one 
sending its blood to the lungs, and the left 
one forcing blood into the aorta. 

The ventricles are strong, and when they 


102 SECOND BOOK OF PHYSIOLOGY 

contract they cause a movement which is called 
the heart-beat. 

If the ear be pressed against the chest, right 
over the heart, the closing of the heart’s valves 
can be heard. Their sounds are nearly like 
loob-dup. 

Work and rest of the heart. —The heart 
must work hard, day and night, from the 
beginning to the end of one’s life. It beats 
about seventy times every minute. Some¬ 
times more and sometimes less. 

The heart does not seem to rest at all ; but 
it does rest nearly half the time, though its 
periods of rest are only the short times be¬ 
tween heart-beats. 

The heart needs a great deal of food to keep 
it strong for the hard work it has to do. It 
does not get food from the blood inside of it, 
but the first artery that branches off from the 
aorta carries fresh blood to the muscles of 
the heart. 

Good blood. —Good blood and a good cir¬ 
culation are almost sure to keep the body in 


CIRCULATION OF BLOOD 


103 


good health. The body may continue to live 
when the blood is poor, but it cannot be 
strong and healthy. Several things are needed 
to make good blood. 

(1) Sufficient food of the proper kind must 
be digested every day and taken into the cur¬ 
rent of blood. The blood can get only what 
we eat and digest for it. If we eat poor food, 
the blood will feed it to the cells, and, of 
course, the whole body will have to suffer. 

(2) Blood is not good unless it contains 
plenty of oxygen. The oxygen we breathe 
is just as important as the food we eat. 

(3) Some waste matter is constantly being 
produced by the action of the muscles and 
nerves, and this goes into the current of blood. 
The blood would soon become very impure if 
it were not for the work of the liver, lungs, 
kidneys, and other organs, that take these 
impurities out and purify the blood. 

(4) The nerves must be able to control the 
size of the arteries, so that the right amount 
of blood will be carried to the place where it 


is most neeaea. 


io 4 SECOND BOOK OF PHYSIOLOGY 

How exercise helps circulation. —We 

have explained that blood will be sent out to 
different parts of the body in proportion to 
their needs. If the right arm is made to work 
harder than the left one, more blood will flow to 
it. The more work the cells do, the faster they 
use up their food, and so they need more blood. 

Now, if one takes some active exercise in 
which many muscles are made to do work, 
more blood will be needed in many parts of the 
body. The arteries will become larger and 
the heart will beat faster. Every organ of the 
body is aroused to activity. The food is rapidly 
used up and a sensation of hunger begins. 
Hunger is simply the call for more food. 

• 

Alcohol and the heart. —When alcohol i§ 
taken into the body, it makes the heart beat 
more rapidly. In some cases of sickness, 
when the heart gets very weak and is unable 
to keep the blood going, doctors give some 
brandy or whiskey to stimulate its action. 
This makes some people think that alcohol is 
good for the heart; but it is found that, after 


CIRCULATION OF BLOOD 


io 5 

the excitement caused by the alcohol has 
passed away, the heart is weaker than before. 

This is the reason some good doctors will 
not give alcohol for any kinds of sickness. 

After one has used beer, whiskey, or other 
alcoholic drinks for a long time, the heart 
often becomes weak and unable to keep up a 
good circulation. This is because some of 
the muscles in the walls of the heart change 
to fat. Fat is not able to do any work, and 
so the heart loses its ability to force the blood 
through its circuit in the body. 

Alcohol and arteries. —The size of the 
arteries is controlled by the nerves. If the 
nerves do not act, the arteries will stand wide 
open. Some parts of the body will then get 
too much blood, and other parts not enough. 

A large dose of alcohol will paralyze the 
nerves for a time, and then there is no way to 
regulate the flow of blood. 

This can be seen in the red face and nose, 
and the bloodshot eyes of the drunkard. 

When one is exposed to cold weather, the 


io6 SECOND BOOK OF PHYSIOLOGY 


blood-vessels in the skin should contract and 
keep, the blood within the body. But alcohol 
will take away this power of the nerves, and 
the blood can flow close to the skin. This 
seems at first to make the body warmer ; but 
the heat is rapidly getting away, and after a 
time the whole body will be colder than it 
would have been without the alcohol. 

Alcohol and blood. —We have already 
explained what is needed to make good blood. 
Unless digestion is good, the blood will not 
be good, and we have seen how alcohol inter¬ 
feres with digestion. Unless the liver, lungs, 
and kidneys keep the blood pure, it will carry 
harmful substances to the cells. Alcohol 
hinders the work of these organs and gives 
them more work to do. 

Tobacco and circulation. —It is claimed 
by good physicians that much of the heart 
trouble and heart failure is caused by the use 
of tobacco. The nicotine in tobacco makes 
the heart palpitate and beat in an irregular 


manner. 


CIRCULATION OF BLOOD 


107 


This effect is most plainly seen in young 
people, who, if they use tobacco at all, are 
almost sure to use it to excess. 

The effect on the blood and the organs of 
circulation soon shows in the bad health of 
the whole body. 

QUESTIONS. 

1. Why is it necessary for the blood to circulate? 

2. How does the blood get the food which it carries 
to the cells? 

3. Describe the liver. 

4. What three things does the liver do ? 

5. What is the thoracic duct, and of what use is it ? 

6. What are the organs of circulation ? 

7. What does the heart do? 

8. Where is the heart ? 

9. What is the pericardium ? 

10. What is meant by right heart and left heart? 

11. Describe the cavities of the heart. 

12. Make a drawing and explain the operation of a 
set of valves. 

13. Why are valves needed in the heart ? 

14. How many valves in the heart ? Name them. 

15. What are arteries ? 

16. What is the aorta ? 

17. What happens in the capillaries ? 


108 SECOND BOOK OF PHYSIOLOGY 

18. Where do veins begin ? 

19. What is the difference between an artery and a 
vein ? 

20. Why are valves in veins ? 

21. Into which cavity of the heart do the veins empty 
the blood ? 

22. Which part of the heart has only red blood ? 

23. What three things does blood do? 

24. What makes the blood red? 

25. What do the red corpuscles do ? 

26. When does blood become purple ? 

27. How can the red corpuscles be seen? 

28. What are white corpuscles ? 

29. What do white corpuscles do ? 

30. Explain the use of a blood-clot. 

31. How many times does a pulse beat ? 

32. What causes the pulse ? 

33. How can the beating of the pulse be made visible ? 

34. How is the flow of blood regulated ? 

35. When the heart beats, what is it doing? 

36. What sound does the heart make? 

37. What is necessary to make good blood ? 

38. How does exercise affect circulation? 

39. What effect does alcohol have on the heart ? 

40. How does alcohol affect the arteries? 

41. How does alcohol cause the blood to be impure? 

42. What is the effect of tobacco on circulation ? 



CHAPTER VI 


RESPIRATION 

Need of air. —Man and all animals need 
air as well as food. Neither one would be of 
any use without the other. We must con¬ 
stantly live in the air, and must breathe a 
large quantity of it into the lungs every day. 
We can eat enough at one time to last for 
several hours, but we cannot keep from 
breathing for even one minute. Because the 
body is all J:he time surrounded by air, it is 
not necessary for us to have any way of stor¬ 
ing it up. 

The part of the air that we need most is 
the oxygen. Oxygen is the very breath of 
life, and we have to depend upon it for every 
minute of our existence. 

The operation of breathing, and the pur¬ 
pose of air in the body, will be explained in 
this chapter. 

109 


iio 


SECOND BOOK OF PHYSIOLOGY 


What respiration is. —Respiration is only 
another name for breathing. Inspiration is 
the act of taking air into the lungs. Ex¬ 
piration is the act of breathing air out of 
the lungs. The two together are called res¬ 
piration. 

We have said that food is like the coal 
which burned under the boiler of a steam-en¬ 
gine. Breathing is like the draft of air which 
makes the coal burn. 

In the steam-boiler the air enters at one end, 
and the smoke and gases are carried away by 
a smoke-stack at the other end. 

In the body the fresh air goes in through 
the windpipe and the bad air comes out the 
same way. 

It is the oxygen in the draft of air that 
makes the coal burn under the boiler, and 
that produces the heat and power of the 
engine. 

It is the oxygen in our breath that makes 
the food in the cells slowly burn, and that 
warms the body and gives us ability to do 
work. 


RESPIRATION 


hi 


Combustion in the body. —Combustion 
is the union of oxygen with other substances. 
If this goes on very rapidly, we say the sub¬ 
stance is being burned, and a blaze is pro¬ 
duced, as in the combustion of wood and coal. 
A great number of substances will unite with 
oxygen in this way ; but the combustion of 
some substances is very slow, and so they 
never get very hot. It is this slow kind of 
combustion that takes place in the body. 

Experiment io. —Secure two pieces of 
magnesium ribbon, each about two inches long. 
Hold one piece with a pair of pliers and light 
it with a burning match. It will burn brill¬ 
iantly, but in a second or two it will all be con¬ 
sumed except some white ash. 

Place the other piece in an open wide¬ 
mouthed bottle and sprinkle upon it a few 
drops of water. In a week or two it will also be 
consumed, and only the white ash will remain. 

In both cases the magnesium was burned 
up by uniting with oxygen. The same amount 
of heat was given out in both cases. 


I I 2 


SECOND BOOK OF PHYSIOLOGY 


This will illustrate what is meant by the 
slow combustion of food in the body. The 
food does not burn as a match burns, but 
more like the magnesium in the bottle. 

Why we need to breathe. —Many of the 
very small animals have no lungs and do not 
breathe. But they must have oxygen, and 
they take all they need right through the sur¬ 
face of their bodies. Even a frog can get a 
good part of his oxygen through his skin. In 
man and all the other warm-blooded animals, 
so much oxygen is needed that there must be 
special organs to get the oxygen into the 
blood. So we breathe it into the lungs, and 
there the red corpuscles of the blood take it 
up and carry it out to the cells in every corner 
of the body. It is in the cells where the slow 
combustion of the food occurs. 

Organs used in respiration. —The or¬ 
gans used in breathing are the nostrils , the 
pharynx , the larynx (voice-box), the trachea 
(windpipe), the bronchi , the bronchial tubes , 
and the air-sacs . The air is forced in and out 




RESPIRATION 


TI 3 

through these passages chiefly by movements 
of the ribs and diaphragm. 

All of the air-passages are lined 
with mucous membrane, and 
nearly all the cells on the surface 
of this membrane have cilia, as 
shown in Fig. 24. The use of 
the cilia will be explained a little 
farther on. F,G - 2 4--Ciliated 

cells. 

The nostrils. —The nostrils have several 
important uses, but they are chiefly intended for 
the entrance of air into the body. Several 
things show that air should always be inhaled 
through the nose and not through the mouth. 

(1) The mucous membrane of the nose is 
always moist with a sticky mucus, which is 
made by the mucous glands. The dust and 
minute living germs, some of which are al¬ 
ways floating in the air, are stopped in the 
nostrils by the mucus. Thus the nostrils act 
as a strainer of the air. 

(2) A thick net-work of blood capillaries is 
just under the mucous lining, so that a large 





11 4 SECOND BOOK OF PHYSIOLOGY 

supply of warm blood always circulates about 
the air as it is entering the body. In this way 
the air is warmed before it reaches the lungs. 

(3) The nerves of smell are located in the 
nostrils, and that, too, shows that the air 
should be breathed only through the nose. 

The larynx. —The air passes through the 
nostrils into the pharynx, which is the box 
described on page 52. Here the air enters 
the larynx. 

The larynx is the voice-box at the top of 
the windpipe. It is made of cartilage, and 
can be plainly felt just under the - chin. 
“Adam’s apple” is a projection of, one of 
the cartilages of the larynx. 

Two membranes, called the vocal cords, are 
stretched across the larynx. The slit between 
the cords is the glottis. In ordinary breathing, 
the glottis is wide open, as shown in Fig. 25. 
When we wish to use the voice in speaking 
or singing, the cords are drawn close together, 
and air from the lungs is forced through them. 
The air makes' the cords vibrate, and thus the 





ll 5 


Fig. 25.—The larynx. E, epiglottis; A, “ Adam’s apple.’ 




Fig. 26.—Vocal cords. V V, true vocal cords; P P, false vocal 
cords ; Z, epiglottis. A, cords open, as in breathing ; B, cords drawn 
close together, as in speaking and singing. 







Hi6 SECOND BOOK OF PHYSIOLOGY 


sound is produced. When the cords are thick 
.and long, the voice will be deep and heavy ; 

when they are short and 
thin, the voice will have 
a high pitch. 

Experiment 11. — 

Get from a dentist some 
rubber, such as he uses 
for rubber dam. Stretch two pieces over the 
end of a lamp-chimney, or tube of any con¬ 
venient size, so that the edges are very nearly 
together. Close the mouth over the end, A, 
and blow through the tube. Stretch the rub¬ 
ber more tightly and notice that the pitch of 
the sound will be raised. 

Tie the rubber in place, and then place both 
hands about the end, 7 ?, so as to make a cavity 
like the mouth. By openi ig and closing the 
hands, while blowing through A , try to make 
the apparatus say mamma. This will illus¬ 
trate the operation of the cords and mouth in 
speaking. 



Fig. 27. — Apparatus to 
illustrate the action of the 
vocal cords. 








RESPIRATION 


11 7 

The trachea and bronchi. —The trachea , 
or windpipe, is a tube about one inch in diam¬ 
eter and four and one-half inches long. At 



its lower end it branches to the right and left, 
forming the two bronchi , one of which goes to 
each lung. 










118 SECOND BOOK OF PHYSIOLOGY 


The trachea is kept open all the time by 
rings of cartilage. These are shown in Fig. 28. 

The whole trachea and bronchi are lined 
with mucous membrane, with its ciliated cells. 
The cilia are hairlike projections which con¬ 
stantly wave back and forth, but their motion 
upward is faster than the motion downward. 

In that way any phlegm or small particles 
that get into the windpipe are moved towards 
the throat, where they can be coughed up. 



Fig. 29. — Bronchial tubes. 


Bronchial tubes. —The bronchi reach to 
the lungs and there they divide into many 
branches, forming the bronchial tubes. These 
divide into finer and finer branches, and at last 



RESPIRATION 


119 

end in an expansion called the air-sac. A few 
of these sacs are shown in Figs. 29 and 31. 
When we take a deep breath, all the sacs are 
filled with air. There are more than four 
million of air-sacs in the lungs. 

The lungs. —The two lungs, the right and 
left, nearly fill the chest. The right one is a 



Fig. 30.—The lungs. 


little larger than the left, the two weighing 
about three pounds. 

The lungs are a kind of spongy substance, 
being made up of bronchial tubes, air-sacs, 
and numerous arteries and blood capillaries. 




120 


SECOND BOOK OF PHYSIOLOGY 


The walls of the air-sacs are very thin, and 
the blood flows through capillaries just outside, 



Fig. 31.—Air-cells. 


so the oxygen can easily go through to the 
blood, and some impurities in the blood can 
come out into the air-sacs. 

The lungs are covered with a smooth mem¬ 
brane called the pleura. 

Inhalation. —Inhalation is the act of filling 
the lungs with air. Air presses with the same 
force in all directions, and so, if the chest be 
made larger, the air will rush in until the press- 





RESPIRATION 


ure inside is the same as 
that outside. The chest 
is changed in size by the 
action of the ribs and dia¬ 
phragm. 

The ribs do not run 
straight around the chest, 
but are lower in front than 
they are behind. If they 
be raised in front, the 
chest will be made larger. 

This action is plainly 
shown in Fig. 32. 

The diaphragm is a 
strong partition of gristle 
and muscle. It stretches 
clear across the trunk of 
the body and forms the 
floor of the chest. It is 
bulged up in the centre, 
and has a shape something 
like a butter-bowl turned the Elevation 
upside down. When the raakes more 

r # chest. 

muscles around its edge 




















122 


SECOND BOOK OF PHYSIOLOGY 


contract they make it flatter, and the chest is 
in that way made larger. 

The ribs and diaphragm work together in 
this manner every time we take a breath. 

Exhalation. —Exhalation is the act of forc¬ 
ing air out of the lungs. This is done by 
making the chest smaller. The ribs sink down 
in front and the diaphragm bulges up. Very 
little effort is needed in ordinary breathing ; 
but when we wish to breathe out a large amount 
of air suddenly, as when we loudly call or 
sing or blow, the muscles in the abdomen push 
the liver and stomach hard against the dia¬ 
phragm. This pushes the diaphragm up and 
forces the air out of the lungs. 

Amount of air in the lungs. —The lungs 
of a man will hold about 330 cubic inches of 
air, but in ordinary, quiet breathing only about 
30 cubic inches are inhaled and exhaled at 
each breath. After the lungs are filled full, 
one can breathe out 230 cubic inches of it, 
but 100 cubic inches always remains in the air- 
cells. 


RESPIRATION 


123 


When one is at rest he can get enough 
oxygen without filling the cells at every breath, 
but when he is at hard exercise he must 
breathe deeply and about twice as fast. This 
is because food is being rapidly consumed in 
doing hard work, and so more oxygen must 
be supplied. It is like turning on a good draft 
of air to get up steam when a locomotive has 
to pull a train up grade. 

A man will breathe about 18 times a minute 
when at rest, but more than 30 times while at 
hard work. The weight of the air that is 
breathed in a day is seven or eight times as 
great as the weight of the food that is eaten. 

Experiment 12. —Count the number of 
times you breathe in one minute. Then run 
one hundred yards and back, and count again. 
This may be made an interesting exercise in 
class. Let one or two keep time while each 
pupil counts the number of breaths he takes 
in a minute. Then let the class arise and take 
some vigorous physical exercise and count 
again. 


124 SECOND BOOK OF PHYSIOLOGY 

Experiment 13. —Make up a good soap 
solution such as can be used in blowing large 
bubbles. Take a full breath and blow as 
large a bubble as you can with one breath. 
Let some one hold a ruler close to the bubble 
while you are blowing and measure as nearly 
as possible the diameter of the bubble when 
it is largest. Then calculate the size of the 
bubble in cubic inches, and you will have the 
amount of air breathed out in one breath. 

Composition of air. —The air is composed 
of several different gases, all well mixed to¬ 
gether. When we breathe the free out-door air 
we always inhale some of each of the gases. 

The great bulk of the air is oxygen and 
nitrogen. About one-fifth of all the air is 
oxygen, and four-fifths nitrogen. 

The four gases of the air are oxygen , nitrogen , 
argon , and carbon dioxide , and they are present 
in these proportions. 

Per Cent. 

Oxygen, 21 
Nitrogen, 78 
Argon, 1 
Carbon dioxide, 0.03 





RESPIRATION 


125 


Oxygen.— Oxygen is the most important 
of all the gases in the air. We breathe the 
air to get the oxygen that it contains. It is 
the oxygen that makes the coal, wood, oil, and 
many other substances burn. It is the oxygen 
that combines with the food in our bodies, and 
gives us ability to do work and also keeps us 
warm. 

Oxygen is a very active gas and will unite 
greedily with many other substances. We 
have to keep a fire department to prevent the 
union of oxygen with the material of our stores 
and homes. 

Experiment 14.— Light a short piece of 
candle and place it on a smooth table. Cover 
it with a glass tumbler and the candle will soon 
“ go out.” We may say that it died because 
it could not get its breath. Water will put 
out a fire by covering the burning material so 
that the oxygen cannot get to it. 

Nitrogen.—Nitrogen forms the largest 
bulk of the air, but it is not active. It will 


126 SECOND BOOK OF PHYSIOLOGY 


put a fire out. Its chief use in breathing is to 
keep us from getting the oxygen too rapidly. 

The nitrogen is breathed into the lungs and 
then exhaled without any change. 

Argon is very much like nitrogen, only even 
less active. 

Carbon dioxide. —There is only a very 
small per cent, of carbon dioxide in the air, 
but it has some very important uses. It is a 
food for all plants. All animals live on plants, 
so that, indirectly, carbon dioxide is a food of 
animals. 

Man and other animals breathe in the oxy¬ 
gen and breathe out the carbon dioxide. Plants 
breathe in carbon dioxide through their leaves 
and breathe out oxygen ; so each throws out 
into the air what the other wants. 

The exchange in the air-cell. —When 
wood and coal are burned, a large amount of 
carbon dioxide is given off in the form of a 
gas. This is carried up the chimneys of our 
houses and factories and escapes into the air. 



RESPIRATION 


127 


When the food is burned within the body this 
same gas is always produced, and the body 
must get rid of it in some way. 



Fig. 33.—Exchange of gases between air and blood.. 

While the fresh red blood is flowing through 
the capillaries of the body it gives up its oxy¬ 
gen to the cells, and takes up in exchange the 
carbon dioxide. The blood is then purple in 
color and starts back at once for the heart* 
which sends it to the lungs. 

In the lungs the purple blood is made to 
pass through fine capillaries just outside the 
air-sac. The carbon dioxide in the blood can 



128 SECOND BOOK OF PHYSIOLOGY 


then pass out into the air-sac, and at the same 
time the oxygen in the air-sac can pass into 
the capillaries to the red corpuscles. 

When the expired air is examined it is found 
that the nitrogen and argon have not been 
changed, but much of the oxygen was taken 
out of it and much carbon dioxide added to 
it. The per cent, of oxygen being now 15 
and of carbon dioxide 4. 

Experiment 15. —Slack a piece of lime 
and put a large handful of it into a quart of 
water in a jar. Shake and set aside till the 
lime settles. The liquid will become clear in 
an hour or two. Carefully pour off some of 
the clear liquid into a test-tube or bottle. Blow 
into it through a glass tube or rye straw. Soon 
the clear liquid will have a milky appearance. 
This is a test for carbon dioxide. If pure air 
had been blown through the tube, the liquid 
would have remained clear. 

How air is made impure. —The air in the 
open country is nearly always good to breathe 


RESPIRATION 


129 


because the volume of air is so large that any 
small impurities would not be noticed. 

The air in living rooms, school buildings, 
public halls' churches, and railway carriages is 
most liable to be impure. If these rooms are 
tightly closed, then there is only a limited 
quantity of oxygen within. 

When the room contains a number of peo¬ 
ple, each will use some of the oxygen at every 
breath and breathe out some carbon dioxide. 
In a short time the air will be unfit to breathe, 
as will be shown by the drowsiness, headache, 
or restlessness of the occupants of the room. 
This is caused not only by the scarcity of 
oxygen and the presence of a large amount of 
carbon dioxide, but the exhaled breath also 
contains some poisons which make the air in a 
close room unfit to breathe. Burning lamps 
also use up the oxygen and give off carbon 
dioxide, but they do not poison the air as 
much as our own breath does. 

Particles afloat in air.— The air always 
contains many living germs and fine particles 


9 


! 3 o SECOND BOOK OF PHYSIOLOGY 

of dust. Even when the air looks perfectly 
clear, it is filled with fine particles that are too 
small to be seen except by aid of the micro¬ 
scope. The fine particles of lifeless matter in 
the air cannot do much harm, for the most of 
them are caught in the nostrils and air-pas- 



Fig. 34.—Dust in air. 


sages before they reach the lungs. When air 
is very dusty it should be avoided, because it 
will irritate and inflame the mucous membrane 
of the air-passages. 

The greatest danger in breathing dusty air 
is not because of the dust itself, but because 
of the minute living germs which are quite 
likely to be floating with the dust. The little 
germ which is most likely to be floating in the 
air is the one that causes consumption, of the 




RESPIRATION 


I 3 I 

lungs. These are so small that it takes a very 
strong microscope to see them. Fig. 34 shows 
how they look. The sputum of a consump¬ 
tive is full of these germs, and, if it dries on 
the street or elsewhere, the wind will drive it 



Fig. 35.— Bacteria of consumption. 


about with the dust. When one breathes 
such air there is great danger that he will get 
the same disease. 

We cannot avoid breathing some dust and 
some living germs. But we can be careful to 
have the air as free from them as possible. 
Best of all, it is possible to keep the body and 
lungs in such a healthy and robust condition 


132 SECOND BOOK OF PHYSIOLOGY 

that the germs cannot get a lodgement there, 
but will be breathed right out again. 

Ventilation. —The way to keep the air 
fresh is to have a fresh supply coming into the 
room all the time, and the foul air constantly 
going out. This is called ventilation, and 
there are many ways by which it may be done. 

A fire in a stove or fireplace will cause a 
draft which will take considerable air up the 
chimney, and fresh air will then come into the 
room through cracks at the doors and windows, 
but this will be sufficient for only one or two 
persons. It would not be enough for a school¬ 
room or hall. 

Rooms that are heated by hot air are mostly 
well ventilated ; but rooms heated by steam or 
hot water in radiators are mostly poorly ven¬ 
tilated, for the same air stays in the room 
all the time, unless some extra arrangement 
is made for ventilation. 

Good air is as necessary to good health as 
good food. The only way to get good air is 
to give close attention to the ventilation of the 


RESPIRATION 


*33 


room in which you live, particularly in the 
winter time, when the room must at the same 
time be kept warm. Warm air may be just 
as fresh as cold air. 

Each person should be provided with 3000 
cubic feet of fresh air every hour. 



Fig. 36.—Ventilation by window. 


Window ventilation. —It is often neces¬ 
sary to admit fresh air at a window. This 
may be done even in cold weather, without 



























i 3 4 SECOND BOOK OF PHYSIOLOGY 

chilling the air too much, by raising the lower 
sash three or four inches and fitting a board in 
at the bottom. Or, as shown in Fig. 36, a 
still better plan is to fit in below the sash a 
metal box with perforated sides. The box 
may easily be made of zinc and should be 
about one inch thick, four inches wide, and 
long enough to fit into the space below the 
sash. The holes in the sides should not be 
opposite each other, and then no direct draft 
will be felt near the window. 

At times when the wind is strongly blowing 
the ventilation is often sufficient without rais¬ 
ing the window. 

Sleeping-room ventilation. —We breathe 
all night, and it is important that the air in the 
bedroom be kept fresh all night. In some 
hospitals the patients sleep in tents or on an 
open veranda, even in cold weather. The 
abundance of fresh air does them good. 

It is better to sleep in a cold room, because 
then one can open the windows and admit 
plenty of air, and he will provide enough of 


RESPIRATION 


J 35 


covers before he goes to sleep, and so will not 
be chilled during the night. 

Good breathing. —The air in a room may be 
pure, and yet we will not get sufficient oxygen 
unless we can inhale it in the proper manner. 

If one sits in a cramped position, the move¬ 
ments of his chest are hampered. 

A tight bandage or belt about the waist will 
make it impossible to breathe properly. The 
lungs and other organs are pushed out of 
their natural position, and the ribs and dia¬ 
phragm are not free to move. When the 
supply of oxygen is small, the body is weak¬ 
ened ; just as when the draft to a fire is shut 
down, the fire burns low. 

It is not necessary to fill the lungs every 
time we breathe, but at least once each day 
a few minutes should be taken for breathing 
exercises. These should always be taken at 
some place where the air is sure to be pure 
and abundant. Before an open window, on 
the porch, or out in the fields or park, are 
good places for breathing exercises. 


136 SECOND BOOK OF PHYSIOLOGY 


Breathing Exercise. —Take a position 
before an open window. Be sure the clothing 
is light and loose. Stand erect. Slowly raise 
the arms from the sides till the hands meet high 
over the head. While the arms are rising, 
be filling the lungs with air. Hold the air for 
a short time. Separate the hands and slowly 
lower them to the side, at the same time 
exhaling the air. Repeat this till you feel a 
little dizzy. This exercise should be repeated 
every morning on arising from bed, or at some 
regular time, till it becomes a habit, and then 
it will not be neglected. 

This is only one of many valuable breathing 
exercises. The value in any of them consists 
in “ keeping them up.” 

Effect of alcohol on breathing. —Good 
health depends very much upon good breathing 
and the perfect oxidation of food, just as a good 
fire depends on. a good draft. Both the 
breathing and the circulation are regulated 
every moment by nerves from the brain. 
Alcohol in large doses, or by continued use of 


RESPIRATION 


i37 


small doses, interferes with this nervous con¬ 
trol. ' The capillaries of the lungs relax. They 
become crowded with blood. This causes, 
inflammation, and the air-cells are crowded so> 
they cannot properly expand. 

Extra work is at the same time, thrown 
upon the lungs, in getting rid of the alcohol 
and other poisons which are caused by the 
alcohol. 

The lungs at all times have enough to do in 
giving oxygen to the blood and casting out 
the waste which is all the time being produced 
in a healthy body. Alcohol adds to the work 
of the lungs, and at the same time decreases 
their ability to do it. 

Anything that interferes with and hinders 
the work of an important organ, such as the 
lungs, weakens the whole body. At such 
times the body is less able to fight off the 
disease germs which are trying to get into it. 
The white corpuscles which guard the body 
are weakened by the alcohol. 

An old drinker will take disease easily, and 
it is hard for him to get well. 


138 SECOND BOOK OF PHYSIOLOGY 

Tobacco smoke and the lungs. — It 

would be better if no one used tobacco in any 
way. Like other narcotics, tobacco has the 
power to set up an appetite that calls for con¬ 
tinually increasing amounts. Hence tobacco 
is seldom used with moderation by those 
whose work is such that they can smoke at 
the same time, and so it often does serious in¬ 
jury to the throat, lungs, and other organs of 
the body. 

The greatest injury done by tobacco is from 
its use by youth who are still growing. There 
is no doubt that the growth of both the body 
and the mind of a boy are stunted by the use 
of tobacco in any form. This is clearly shown 
by the facts which have been gathered in a 
great many cases and during a long time. 

By far the worst use of tobacco is the smok¬ 
ing of cigarettes. This is chiefly due to the 
manner in which cigarettes are smoked, and 
to the ease with which they may be used to 
-excess. 

The cigarette smoke is nearly always in¬ 
haled, that is, it is drawn down into the air- 



RESPIRATION 


*39 


cells of the lungs. There the poison in the 
tobacco easily passes into the blood, and is 
carried out to the brain, nerves, muscle, and 
all other parts of the body. 

It is very easy to get into the habit ot smok¬ 
ing cigarettes, and it is hard to break away 
from it. 

A boy who smokes cigarettes runs a great 
risk of spoiling his prospects of success in 
life. 


QUESTIONS. 

1. Why do we have to breathe so often ? 

2. What part of the air do we need ? 

3. What is respiration? 

4. What makes coal burn ? 

5. What is meant by combustion? 

6 . Describe an experiment to illustrate slow com. 
bustion. 

7. Why do we have spe'cial organs of respiration ? 

8. Name all the organs used in respiration. 

9. Give two good reasons for breathing through the 
nostrils. 

10. Describe the larynx. 

11. Describe the vocal cords. 

12. Have you performed Experiment 11 ? 


i 4 o SECOND BOOK OF PHYSIOLOGY 

13. Describe the trachea. 

14. What are the bronchi ? 

15. What is the use of the ciliated cells in the wind¬ 
pipe? 

16. How many air-sacs in the lungs? 

17. How does the air get from the bronchi to the air- 
sacs ? 

18. Describe the lungs. 

19. What makes air go into the lungs? 

20. What forces air out of the lungs ? 

21. How can we make the voice very loud ? 

22. How much air will the lungs hold? 

23. Why do we breathe faster when we are hard at 
work ? 

24. How many times do you breathe in one minute? 

25. How can you count the number of cubic inches of 
air in one breath ? 

26. Name four gases in the air, and tell how much of 
each kind. 

27. Which is the most important gas? Why? 

28. What does the nitrogen do? 

29. What is the use of the carbon dioxide ? 

30. What exchange is made between the blood and 
the air in the air-sacs ? 

31. Have you tested for carbon dioxide in your 
breath ? 

32. Why is it harmful to breathe dust ? 




RESPIRATION 


141 

33. How are consumption germs carried in the air? 

34. What is ventilation ? 

35. Tell several ways of ventilating rooms. 

36. What is good breathing ? 

37. Describe some good breathing exercise. 

38. How does alcohol injure the organs of breathing? 

39. Why is cigarette smoke so injurious to the body? 


Directions for Disinfection 

A room or enclosure of any kind may be easily, thoroughly, 
and cheaply disinfected by use of formaldehyde gas rapidly gener¬ 
ated by a mixture of potassium permanganate and formalin. 

The gas will not injure the furniture, carpets, curtains, or 
other like contents of the room. It is well to disinfect a room occa 
sionally even though it is not suspected of containing germs of a 
contagious disease. 

The following method is recommended : 

For each 2000 cubic feet of air-space in a room use about 670 
grams or pounds of formalin. Place this in a bucket and place 
the bucket in a tub in the centre of the room. Pour into the 
formalin in the bucket about 330 grams or & pound of the per¬ 
manganate. These amounts need not be exact, but about this 
amount of each should be used for each 2000 cubic feet of air-space. 
Leave the room at once and close the door. Of course all windows 
and doors must be closed as tight as possible. The purpose of 
the tub is to prevent injury to the carpets or floor, for the gas is 
generated so rapidly that the contents of the bucket may flow over. 
The closets within the room should be open. Bedding and gar¬ 
ments that have been actually exposed to contagious disease 
should be burned, but light garments that can be completely ex¬ 
posed to the formaldehyde by being loosely spread out may be 
disinfected. The room should remain closed for at least two hours. 
The windows should then be thrown open and the room well 
ventilated. 



CHAPTER VII 


THE SKELETON 

Use of the skeleton.—The skeleton is the 
bony frame-work of the body. It has several 
important uses. 

(1) It fixes the shape of the body. No 
matter whether we lie down or stand, the 
bones keep the body about the same height 
and shape. 

(2) Bones protect many of the delicate parts 
of the body from injury. The skull surrounds 
the delicate brain, and the ribs protect the 
heart and lungs. 

(3) Bones support many of the softer parts 
of the body and hold them in place. The 
organs in the thorax and abdomen are sup¬ 
ported from the ribs and backbone. 

(4) Many of the bones are used as levers 
to give motion to the body. The forearm is 
used as a lever when we bend the arm at 
the elbow and move the hand back and forth. 


142 



THE SKELETON 


J 43 


If it were not for the bones, the motions of 
our body would be slow and sluggish, and we 
could only crawl around. 

Kinds of bones.—There are in all 206 
different bones in the adult human body. 
These may all be put into four classes. The 
long , short , flat, and irregular bones. The 
bones in the legs, arms, and’ hands are long 
bones. Those in the wrist and ankles are 
short bones. Those in the skull, the ribs, the 
shoulder-blade, are examples of flat bones. 

The irregular bones are such as have an ir¬ 
regular shape, like the vertebrae of the back¬ 
bone. 

The cranium.—The cranium is a strong 
bony box which protects and supports the 
brain. It is made of several flat bones, which 
are joined together at the zigzag lines shown 
in the cut. This kind of joint is called a 
suture , because the bones seem to be sewed 
together. 

There are 8 bones in the cranium : 


M4 


SECOND BOOK OF PHYSIOLOGY 


1 frontal, the forehead. 

2 temporal, at side of head, just above the ears 
2 parietal, one on each side, back of frontal. 

i occipital, at lower part of back of head. 

i sphenoid ) „ . , _ 

[■ forming the floor of the cranium, 
i ethmoid ) 



The spinal column.—A vertebra is one 
of the bones of the spinal column. One is 
shown in Fig. 38. It has a number of proc¬ 
esses which extend backward and sideways. 
a, Fig. 38, is the process which can be felt 
when you rub your fingers along the back¬ 
bone. 

Through each vertebra is a hole, so that, 



THE SKELETON 


i45 


when they are placed one on top of another, 
the holes form a long tube. In this tube is 
found the spinal cord, sometimes called the 
marrow. 



Fig. 38.—A vertebra. 


The spinal column is formed ot 26 separate 
bones, put together so as to form a column, 
as shown in Fig. 39. This column supports 
the head and body, and makes it possible for 
us to stand erect. There are five classes of 
bones in the spinal column : 

7 cervical vertebrae, in the neck. 

12 dorsal vertebrae, in the back. 

5 lumbar vertebrae, in the small of the back. 


146 second book of physiology 



Fig. 39.—Backbone. 


THE SKELETON 


147 


1 sacrum, made of five bones which grow together 
into one bone called the sacrum. 

1 coccyx , at lowest point of the spinal column, made 
of four bones which grow together into one bone called 
the coccyx. 

These are named in order from the top 
down. 

The topmost cervical vertebra is called the 
atlas , and the next one, the axis. The head 



rests on the atlas, and the atlas can freely 
turn on the axis. A pivot from the axis runs 
up through the atlas and holds it in place. 
The position of these two bones is shown in 
Fig. 40. 


i 4 8 SECOND BOOK OF PHYSIOLOGY 

How the vertebrae are joined together. 

—It can be seen in Fig. 39 that the backbone 
is curved a little like the letter S. This helps 
to prevent any sudden jars to the head and 



Fig. 41.—Section through two vertebrae, showing pad of cartilage, I. 

the organs of the chest. If the backbone 
were straight up and down, then the jar from 
jumping and running would be greater. 

There is also an elastic pad of cartilage 
placed between the vertebrae, as shown in 
Fig. 41. The bones do not touch each other. 
Each pad is elastic like rubber, and so they 
act like a spring under a carriage to prevent 
jolting. They also make the backbone very 
flexible, so that we can easily bend the body 
in any direction. 



THE SKELETON 


149 


The ribs.—The ribs are flat elastic bones 
that form the frame-work of the chest. There 
are 24 ribs, 12 on each side. One pair of 
ribs is jointed to each of the dorsal vertebrae. 



Fig. 42.—The ribs. 


as may be seen in Fig. 42. In the front they 
are attached to the breast-bone by a flexible 
cartilage, except the two lower ones, which are 
not fastened in front. 

The pelvis.—The pelvis is a large bony 
basin at the bottom of the trunk of the body. 




150 SECOND BOOK OF PHYSIOLOGY 



Fig. 43.—The pelvis. 



Fig. 44.—The scapula. 





THE SKELETON 


It is made up of the sacrum and coccyx, which 
have already been explained as forming the 
lower end of the spinal column, and the large 
hip-bones, one on each side. 

The collar-bone and shoulder-blade.— 

The collar-bone is a long bone running from 
the top of the breast-bone out to the shoulder. 
It is called the clavicle. There is one on each 
.side. 

The shoulder-blade is a broad, flat bone, 
shaped as in Fig. 44. It is called the scapula . 
There is one just back of each shoulder. 

Bones of the arm and hand.—There are 
30 bones in each arm. They are: 

1 humerus, between shoulder and elbow. 

2 radius and ulna , between elbow and wrist. 

8 carpal bones , in the wrist. 

5 metacarpal bones , in the hand. 

14 phalanges, in the fingers. 

The humerus is the largest bone in the arm. 
At its upper end it forms a joint with the 
shoulder-blade, at d, Fig. 44. At its lower 
end it is jointed to the radius and ulna. 


*5 2 


SECOND BOOK OF PHYSIOLOGY 


The radius and ulna lie side by side be¬ 
tween the elbow and wrist. 

The radius is on the same 
side as the thumb. When the 
hand is turned so that the 
palm is down, the two bones 
lie across each other. 

In each wrist there are 8 
short bones. They are, to- 



Fig. 45.—Bones of 
arm and hand. 


Fig. 46.—The carpus. 


gether, called the carpus . Just below the 
carpus are the five metacarpal bones , and then 
th e. phalanges. Each finger has three bones, 
and the thumb, two. 






THE SKELETON 


J 53 


Bones of the leg and foot. —The bones 
of the leg and foot are much 
like those in the arm and hand, 
but they have different names. 

Naming them from the hip 
down, they are : 

1 femur , between the hip and the 

knee. 

2 tibia and fibula, between knee 

and ankle. 

7 tarsal bones, in ankle. 

5 metatarsal bones, in body of foot. 

14 phalanges , in toes. 

1 patella , the knee-pan. 

This makes 30 bones in each 

leg. 

The femur is the largest bone 
in the body. At its upper end 
it is jointed to the hip-bone, 
and at its' lower end to the 
tibia and fibula. The tibia and 
fibula lie side by side between 
the knee and ankle. The tibia 
is the shin-bone, and it lies on the same side 



Fig. 47.—Bones of 
leg and foot. 









154 SECOND BOOK OF PHYSIOLOGY 

as the great toe. In each ankle there are 7 
short bones. They are, together, called the 
tarsus. Just below the tarsus are the meta¬ 
tarsal bones, and then the phalanges. Each 
toe has three bones, except the great toe, 
which has two. 

Other bones.—If you will now count all 
the bones that have been named and described, 
you will find you have 184. 
That leaves 22 to be yet 
named to make the 206. 

There are 14 bones in the 
face. These are of various 

Fig. 48.—Hyoid bone. 

shapes and sizes, forming 
a frame-work for the nose, mouth, and cheeks. 

There are three small bones in each ear. 
These will be shown when we explain the ear. 

The breast-bone, called the sternum , is the 
bone to which the ribs are attached in front of 
the chest. 

Last is the hyoid bone , shown in Fig. 48. It 
is located at the base of the tongue. 

This completes the list of 206 bones. 






THE SKELETON 


*55 


Why bones are hard.—Bones are made 
of two kinds of matter. One is called animal 
matter. It is soft and bends easily. The 
other is called earthy matter. It is chiefly 
lime, and makes the bone hard and strong. 
About two-thirds of the bone of a man is lime. 
In some parts of the body, as in the ears and 
the point of the nose, the lime is left out. It 
is then called cartilage, and can be easily bent 
without breaking. The bones of young chil¬ 
dren are soft because there is not much lime 
in them. 

Experiment 16.—Get, at the butcher-shop, 
the rib of a lamb. Clean it of all flesh or fat. 



Fig. 49.—Bone tied into knot. 


Place it in a tall bottle or long dish and cover 
it with water. Then pour into the water about 
two ounces of strong hydrochloric acid. Stir 
or shake it, and then set aside for a day or 
more. The acid will “ eat out ” all the lime, 




156 SECOND BOOK OF PHYSIOLOGY 

and only the soft animal matter will be left. 
The rib can then be easily bent or tied in a 
knot without breaking. 

Experiment 17.—Place a chunk of hard 
bone in the hot part of the fire in a stove or 
furnace. In two or three hours all the animal 
part of the bone will be burned out, and only 
the lime will be left. This part is brittle, and 
will break if struck with a hammer. 



Fig. 50.—Longitudinal section of femur. 


Strength of bone.—The mixture of lime 
and animal matter makes the bones very hard 





THE SKELETON 


*57 


and tough. The shape of the long bones also 
increases their strength. As shown in Fig. 
50, a long bone is a hollow shaft. This makes 
them able to bear a great deal of weight with¬ 
out bending. The ends of long bones are 
larger than the middle part, and are filled with 
a kind of spongy bone. 

The hollow of the shaft is filled with fatty 
marrow. The strongest bones are placed 
where they are most needed. The femur, for 
example, must hold up the body and also 
heavy weights, which are sometimes carried. 

Flat bones, like those in the skull, are 
strong, because they are made of two plates 
of hard bone with spongy bone between. 

How bone grows.—The bone in the body 
is alive. It is composed of numerous cells, 
which build up the bony material. These 
cells are fixed to one place, and so their food 
must be brought to them by the blood. In 
Fig. 51 can be seen the appearance of a very 
thin cross-section of hard bone as it is seen in 
a microscope. The round holes at the centre 


158 SECOND BOOK OF PHYSIOLOGY 


of the circles are the canals through which 
blood is distributed to the cells of the bone. 

The irregular spots which are arranged in 
circles around the canals are the bone-cells. 



Fig. 51.—Microscopic appearance of a section of bone. 


Other very fine canals connect the cells to each 
other and also to the larger canal at the 
centre. 

All bones are covered with a membrane 
called the periosteum . It adheres closely to 
the bone, and contains numerous blood-vessels 
which here and there enter the hard bone and 
pass along the bony canals. 


THE SKELETON 


*59 


Care of bones. —Bones may become dis¬ 
eased just like other parts of the body. Good 
bone cannot be formed unless the blood con¬ 
tains the kind of food that the bones need. 

There is a disease called rickets which is 
common with children whose food is of a poor 
kind or insufficient. The bones of their backs 
and legs are often bent and out of shape. The 
bone-cells are so poorly fed that they cannot 
make strong bone. 

The bones of youth are quite soft, but they 
gradually grow harder and more brittle until 
it is not possible to change their shape. The 
bones of children may be pressed into a 
variety of shapes, and if kept that way, they 
will harden and be fixed in that position. 

Bow-legs are a common misfortune which 
might easily have been prevented by proper 
care in early life, or might have been corrected 
by proper supports while the bone was yet 
soft. 

Tight shoes will deform the bones of the 
foot and cause one to walk in an awkward 
and unsteady manner. 


160 SECOND BOOK OF PHYSIOLOGY 


Stooping shoulders come from careless hab¬ 
its of standing or sitting with the shoulders 
bent forward. The head should be held up 
and the chest pushed forward. This is desir¬ 
able, not only because it looks much better, 
but also because it helps one to breathe 
better and gives him better health. 

Those who sit long in one place should be 
careful of their position. School-desks should 
be of such shape and size that the feet may 
rest on the floor, and the body may not be 
cramped. It is well most of the time to sit 
back on the seat and hold the book in the 
hands, rather than to bend over it. 

Broken bones. —If the bones of children 
were as hard and brittle as those of a man, 
they would often have broken bones from their 
numerous falls and tumbles. But even the 
bones of boys and girls are often broken by 
accident. In such a case it is necessary to call 
a surgeon at once and have the bone set. 
Then it must be kept quiet for five or six 
weeks until the broken ends grow together 


THE SKELETON 


161 


again. It is necessary to have a broken bone 
set and held in place, or it will be long in 
healing, and will be crooked when it does heal. 

Joints of the skeleton. —If there were no 
joints in the skeleton, a man would be a very 
stiff and helpless creature. He might be able 
to stand, but he could not move. If he wished 
to lie.down, he would have to fall over as a 
stick of wood falls. But the numerous joints 
permit a great variety of motions. Count the 
number of joints in the hand alone, and notice 
how necessary they are to the work which 
the hand must do. If the joints of a finger or 
the wrist should become stiff, the hand would 
be very much crippled. 

Kinds of joints. —The two most important 
kinds of joints in the body are the hinge and 
the ball and socket. 

The most common is the hinge-joint. It is 
used in the elbow, the knee, the toes, the 
fingers, and, to some extent, at other joints. 

They are called hinge-joints because they 


162 SECOND BOOK OF PHYSIOLOGY 


allow movement back and forth, like the 
hinges on a door. The elbow-joint, for exam¬ 
ple, permits us to move the forearm in and 
out, but we cannot move it sideways. 



Fig. 52.—Hip-joint. 


The ball-and-socket joint is used where 
great freedom of motion is desired. The two 
best examples are the hip-joint and shoulder- 
joint. As shown in Fig. 52, the ball is at the 
upper end of the femur and the socket is in 
the large hip-bone. This will allow the leg 
to be moved in any direction. 


THE SKELETON 


163 


In the shoulder-joint, the upper end of the 
humerus fits into a shallow socket in the 
scapula. This gives the greatest freedom of 
motion, and the arms can be freely swung in 
all directions. 

There are also several other kinds of joints 
which are well suited for special kinds of 
motion. 

The pivot-joint is like that between the atlas 
and axis which permits a motion of the head 
from side to side. 

The gliding-joint permits a slight slipping 
of one bone on another, as in the wrist and 
ankle. These joints are strong and flexible. 

How joints are formed. —Joints are 
formed by two or more bones which are joined 
end to end. The ends are kept to their 
proper place by strong ligaments which reach 
across from one bone to the other. In Fig. 
53 is shown the ligament that binds the 
humerus to its place in the shoulder. 

This ligament is very strong, and it would 
take a powerful force to break it. 


164 SECOND BOOK OF PHYSIOLOGY 

Other joints are bound by ligaments in a 
similar manner. 

How joints are kept smooth. —The hard 
bones do not touch each other at the joints. 



Fig. 53. —Ligaments of a shoulder-joint. 

If they did, they would wear down and become 
rough. The ends of the two bones that unite 
to form a joint are covered with a pad of 
cartilage. This is very smooth and tough, 
and is always moist with a slippery fluid that 
looks like the white of an egg. It is called 
synovial fluid. It makes the cartilage slip- 



THE SKELETON 165 

pery, and so the joints can be moved without 
friction. 

QUESTIONS. 

1. Give four uses of bones. 

2. Which use do you think most important? 

3. Name four kinds of bones. 

4. Give an example of each of the four kinds. 

5. Name the eight bones of the cranium. 

6. What is a vertebra ? 

7. How is the canal through the spinal column 
formed ? 

8. How many vertebrae in the spinal column ? 

9. Name the classes of vertebrae. 

10. Give the number of each kind of vertebrae. 

11. Describe the atlas and axis. 

12. What is the shape of the spinal column? 

13. What is between the vertebrae? What is its use? 

14. How many ribs are there on each side? 

15. How are ribs fastened at the ends? 

16. Describe the pelvis. 

17. Where are the clavicle and scapula ? 

18. How many bones in an arm and hand? 

19. Name and give the number of the five different 
kinds. 

20. Describe the radius and ulna. 

21. What is the carpus ? 

22. How many bones in the leg and foot? 


i66 


SECOND BOOK OF PHYSIOLOGY 


23. Name and give the number of the six different 
kinds. 

24. Which bone is the tibia ? 

25. What is the tarsus? 

26. How many bones in the face? 

27. How many bones in the whole body? 

28. Name all the bones in your arm as you point to 
them. In the cranium. 

29. Name all the bones you can think of, and count 
as you go. 

30. What are the two kinds of matter in bone ? 

31. Have you performed Experiments 16 and 17? 

32. What makes bone strong? 

33. How does a bone grow? 

34. What is periosteum ? 

35. What is the cause of rickets? 

36. Why are the bones of young children soft? 

37. What causes drooping shoulders? 

3g. Why should a broken bone be set ? 

39. What is the use of joints ? 

40. Name four kinds of joints and give example o* 
each kind. 

41. How are joints held in place? 

42. What is the use of synovial fluid ? 



CHAPTER VIII 


THE MUSCLES 

Movements of the body.—In all kinds 
of animals there is an almost constant move¬ 
ment of some kind. It may be only in the 
cells, or of some part of the body, or the whole 
body. When we try to find out whether or 
not a body is alive, we look for some move¬ 
ment. If we can feel the pulse, we know that 
the blood is moving through the body. If we 
see the chest rise and fall in breathing, we de¬ 
cide that the body is alive. If one moves his 
hand or foot, we take that as a sign of life. 

All such movements of the body are caused 
by muscles. The bones cannot move them¬ 
selves, but the muscles which are attached to 
the bones can use them as levers. 

Two kinds of muscles.—The most im¬ 
portant muscles are those which are attached 
to bones. These are called the skeletal mus- 

167 


168 SECOND BOOK OF PHYSIOLOGY 

cles. They cause the chief motions of the 
body, such as those of the arms, legs, head, 
trunk, and so on. 

Another kind is found in the walls of the 
stomach, intestines, arteries, and heart. These 
are not attached to bones. 

How a skeletal muscle works.—That 
a skeletal muscle may produce motion, it is 
necessary that its ends be fastened to two pieces 



of bone which have a movable joint between 
them. Then, when the muscle contracts and 
becomes shorter, the two bones will be pulled 
towards each other. All the skeletal muscles 
work on this plan. 

Experiment 18.—Get two sticks about one 
inch square, one io inches long and the other 


THE MUSCLES 


169 


12. Fasten them together, end to end, with 
a hinge. Let us call the longer stick the hu¬ 
merus and the shorter one the radius. Then 
the hinge will be the elbow-joint. Fasten a 
cord at I, Fig. 54, and pass it through a hole 
at O. This cord will represent the muscle. 
When the cord is pulled, the shorter stick is 
drawn towards the longer one. This illustrates 
the action of the muscle which raises the hand 
to the mouth. 

How muscles are fastened to bones. 

—The soft red central part of a muscle tapers 




Fig. 55.—Muscle before and after contraction. 

off into a very strong white cord called a ten¬ 
don. Beefsteak is the muscle of the ox, and 
the lean part of pork is the muscle of the hog. 



SECOND BOOK OF PHYSIOLOGY 


170 


These muscles were used by the animal in 
moving itself about when it was alive. 

Sometimes the muscles 
are fastened directly to the 
bone,—that is, they do not 
have any tendons ; but in 
most cases the muscle ends 
in a tendon, and then the 
tendon is attached to the 
bone. 

This arrangement is very 
nicely shown in Fig. 56. 
The muscles which move the 
hand and fingers are placed 
up in the forearm, and long 
tendons run from their lower 
ends down along the wrist 
to the fingers. This allows 
the hand and wrist to be 
small and neat, and at the 
same time very strong. 

A similar arrangement is 
used for the movement of the feet. The 
muscles are there placed in the calf of the 



Fig. 56.—Muscles and 
tendons of amis. 








THE MUSCLES 


171 

leg, and from their lower ends long tendons 
run down along the ankle to the foot and toes. 

The muscles that move the forearm are 
placed up near the shoulder, around the hu¬ 



merus. This muscle is called the biceps. It 
is the one that most boys and men refer to 
when they want to show how strong they are. 
You can see in Fig. 57 how it is attached by 
tendons to the radius at the lower end and 
the shoulder at the upper end. The lower 
tendon is bound down close to the elbow. It 




172 SECOND BOOK OF PHYSIOLOGY 

is plain that when this muscle contracts 
(Fig. 54), the hand will be drawn towards 
the shoulder. These tendons can be easily 
felt on the inner side of the elbow. 

A tendon is so strong that even the bone 
will be broken before the tendon can be pulled 
apart. You can see their strength in a 
butcher-shop where hogs and beef are hung 
up by the small tendon in their hind-legs. 

How muscles are made to contract.— 

All muscles are made up of a great number 
of cells, and fine nerve-fibres connect the cells 
to the brain. When I wish to move one of 
my fingers, for example, the brain sends an 
order down along a nerve to a muscle in the 
forearm. This muscle, then, becomes shorter 
and pulls on the tendon, causing the finger to 
move. Such a muscle is called a voluntary 
muscle , because it can be made to contract 
whenever the mind so wishes. All the skele¬ 
tal muscles are voluntary. They are under 
the control of the will, so that we can make 
them work or rest. 



THE MUSCLES 


*73 


There are also other muscles which are not 
under the control of the will. They are called 
the involuntary muscles. They are made to 
contract by nerves also ; but the mind cannot 
make them rest or work. The heart, for ex¬ 
ample, beats day and night without any attem 
tion of the mind. 

The muscles that cause breathing continue 
their work whether we think of them or not. 
The muscles in the walls of the stomach roll 
the food about while it is being digested, 
though we may give it no thought. 

This is a great advantage to us, for if we 
had to look after all these things, we would 
have little time for any¬ 
thing else, and would 
do the work very poorly, 
besides. 

Fig. 58.—Artery feeding 
muscle. 

Structure of mus¬ 
cle. —A muscle-cell may be an inch or more 
in length, but is so fine that it can scarcely 
be seen without a microscope. A muscle is 
a great number of such cells put together in 



i 7 4 SECOND BOOK OF PHYSIOLOGY 


a bundle. A few cells would have very little 
power, but when millions of them all work 
together, they can lift heavy weights and do 
hard work. 

Each cell receives its supply of food from 
the blood, and when it works, this food is 
used up. Fig. 58 shows how an artery brings 
the blood to the muscle. About one-fourth 
of all the blood in the body is in the muscles. 

Muscles of the head. —There are more 
than 500 different muscles in the human body. 
They all have names, which are sometimes 
long and hard to pronounce. We will not 
try to learn the list now. You can see in 
Fig. 59 the numerous muscles of the face and 
neck. When they are made to contract, they 
cause the various movements of the face and 
head. We use them in smiling, scowling, 
sneering, chewing the food, turning the head, 
and so on. 

We will name a number of movements of 
the head or face, and will ask you to tell by the 
number in the figure which muscle is used : 




the muscles 



*75 

1. Turning the head to the left. 

2. Throwing the head back. 

3. Lowering the chin. 


Fig. 59.-—Muscles of head and neck. 

4. Opening the lower jaw. 

5. Closing the lower jaw. 

6. Smiling. 

7. Sneering. 


176 SECOND BOOK OF PHYSIOLOGY 


8. Puckering the mouth as in whistling. 

9. Raising the eyebrows. 

10. Squinting. 

11. Drawing down the corner of the mouth. 

12. Moving the scalp. • 

The use of these muscles has much to do 
with the expression of the face. A constant 
scowl may become a fixed expression whether 
one so wishes or not, and a pleasing expres¬ 
sion may as easily become a fixed one. 

How muscles are developed. —Muscles 
grow stronger when they are used. The arm 
that does the most work is stronger than the 
other. Any muscle that is unused for a long 
time will lose all its power. More blood 
flows to a muscle when it is at work, and so 
the cells there are better fed. 

Each cell is supplied with food and oxygen 
by the blood, and these two unite in the cell, 
producing the heat and the ability to do work. 
So you can see why more blood would have 
to flow to the muscle that works. It is also 
plain that good, wholesome food and pure air 


THE MUSCLES 


177 


are necessary for the development of good 
muscles. 

Development is slow. —A great number 
of people would like to have strong muscles, 
and they know the benefit of exercise, but 
they make a mistake in trying to get large 
results in a short time. A boy sometimes 
selects a heavy pair of dumb bells, and thinks 
he can make large muscles on his arms in a 
few days. This is all a mistake. All devel¬ 
opment is very slow, and only those who do 
just a little every day, and do it right, can 
expect good and lasting results. It does the 
muscles more harm than good when they are 
worked too hard or too long at a time. 

Kinds of exercise. —The most of those 
who work out of doors all day get plenty of 
exercise, and, as a rule, are strong and healthy. 
But those who spend most of their time in 
stores, offices, or as students in school, need 
to take exercise to keep the body healthy. 

The best games for exercise are those that 


12 



178 SECOND BOOK OF PHYSIOLOGY 

are taken out of doors in the pure air and 
sunshine. The best kinds of exercises are 
those that bring many muscles of the body 
into use. 

Base-ball, tennis, rowing, foot-ball, golf, and 
similar exercises are all good. 

The numerous out-door sports of children 
are necessary to their growth and develop¬ 
ment. 

A stroll about the town is of little value as 
an exercise, but a brisk walk through woods 
and fields is excellent. 

The physical culture which is taught in the 
schools is good because it is taken every day, 
and all the important muscles are made to 
take part. Interest greatly aids in exercise. 

A trained muscle. —The purpose in many 
games and exercises is not only to make the 
muscle strong and healthy, but also to make 
it skilful. 

The muscles of the arm may be very strong 
and yet very awkward. A strong and large 
muscle is nothing to be proud of unless it has 


THE MUSCLES 


179 


been trained so that it obeys the mind. A 
good writer, a good machinist, a good singer, 
or a good ball-pitcher are those who know 
how to do these things, and have practised 
until they can do them well. 

It is a good thing to have strong and 
healthy muscles, but one’s success depends 
more upon his ability to use them with skill. 

A large muscle may be developed often in 
a few months, but it takes a long time to 
develop a skilful muscle. 

Young people sometimes get in a hurry, 
and do not see the necessity of keeping up 
their practice every day, but that is the only 
way people ever learn to use their muscles 
with skill. 

Effect of alcohol on muscle. —Some peo¬ 
ple think that beer, whiskey, and other alco¬ 
holic drinks will make the muscle strong. 
They think they can do more work when they 
take a drink of this kind. This is found to 
be a great mistake. A great many experi¬ 
ments have been tried, and it is always found 


180 SECOND BOOK OF PHYSIOLOGY 

that alcohol will make the muscle less able to 
stand a long period of labor or exercise. 

A drink of whiskey will excite the brain and 
make one think that he is stronger than he is; 

he may then start into 
some work very briskly; 
but he tires sooner than 
when he does not drink, 
and at the end of the 
day he has less work 
done. 

People who drink beer 
often become fat. They 
look as though they 
were very healthy, but 
they are often found 
to have weak muscles. 
There is no strength in fat. It is only an 
excess of food which the body stores up in 
that form. Beer not only makes fat, but it 
does so at the expense of muscle. Part of the 
muscle turns to fat, and, of course, the mus¬ 
cle becomes weak. 

It was once quite common to give whiskey 



Fig. 6o.—F at tissue. 


THE MUSCLES 181 

to soldiers before a long march or a battle, but 
experience has shown that it did the soldier 
more harm than good. He would “give out” 
sooner when he drank alcohol. A little sugar 
is found to do him much more good. The 
best doctors are opposed to the use of alcohol 
for such a purpose. 

Alcohol and the shops. —A great many 
men are at work in the large shops and on the 
railroads. Those who hire these men are 
always anxious to get those who do not drink 
alcohol. Why is this ? There are several 
reasons, (i) One who drinks does not, as a 
rule, have strong muscles, and he will get 
tired long before the whistle blows. Such a 
one will put in his time, but he will not do as 
much work as he would do if he did not drink. 
(2) A drinker is not so skilful in his work. 
His motions are often awkward and his hand 
is not steady. (3) Many drinkers will at times 
get drunk and take a day or more off from their 
work. This may happen at a time when their 
employer most needs them. (4) An employer 


182 SECOND BOOK OF PHYSIOLOGY 


would rather have men who save their money 
and have ambition to succeed. They always 
make better workmen. A drinker wastes his 
money and time, and loses his ambition to 
succeed in life. (5) A drinker is not in every 
way as reliable as one who is sober and 
industrious. 

These are certainly sufficient reasons why an 
employer prefers a man who does not drink. 

The railroad companies are very particular 
about hiring only those men who do not drink. 
A single drink is sufficient reason for his 
discharge. A locomotive engineer must have 
a steady hand, a keen eye, and must be wide 
awake. A very slight mistake on his part 
might cause the loss of many lives and many 
thousands of dollars’ worth of property. 

If the railroad companies have found that 
their men are much better without whiskey, 
beer, or wine, it would be just as true of men 
in other kinds of work. 

Athletics and alcohol. —Young men who 
are preparing for some kind of athletic con- 


THE MUSCLES 


183 

test, such as running, boxing, boating, and 
foot-ball, often hire a trainer. A good trainer 
will insist that the boys drink no alcohol and 
use no tobacco. The reason is very plain. The 
victory in such a contest usually goes to the 
one who can hold out the longest,—the one 
who has the best lungs, heart, and muscle, 
other things being nearly equal. Whiskey 
and tobacco will do more harm than any train¬ 
ing can do good in preparation for a close 
contest. 

Tobacco and muscles. —It is plain that 
tobacco never assists in the growth and devel¬ 
opment of muscle. On the other hand, it 
often hinders them and works a decided in¬ 
jury. It is often noticed that a boy who uses 
tobacco becomes lazy. He does not want to 
be disturbed. He lounges in his seat. He 
leans against any object near him. He 
scrapes his feet when he walks and performs 
his work in a slouchy manner. One reason 
for this is the poisonous effect of the nicotine 
on the nerves and muscles. 


184 SECOND BOOK OF PHYSIOLOGY 


This is one of the reasons an employer will 
not hire a boy for work in his office or store 
if he smokes cigarettes. Any use of tobacco 
will injure the body and mind of a growing 
boy, but cigarette smoking is the most harm¬ 
ful of all. 

Many investigations have been made of 
the effect of tobacco on the boys and young 
men in our schools and colleges. The general 
conclusion is that the use of tobacco stunts 
the development of both the mind and the 
body. Students who constantly smoke the 
cigar, cigarette, or pipe are shorter in stature 
and behind their classes in school. 

Tobacco smoke decreases the capacity of 
the lungs and causes an irregular action of the 
heart. Thus it strikes at the very source of 
the food of the muscles. 

When an employer searches for a boy or 
young man to take an important position, he 
always prefers one who does not use tobacco. 
At least he will make sure that he does not 
smoke cigarettes. There are other strong 
reasons why boys should never get into the 


THE MUSCLES 185 

habit of using tobacco, but we will give them 
in a later chapter. 

QUESTIONS. 

1. What is the common proof that a body is alive ? 

2. How are most of the body’s movements produced ? 

3. What are skeletal muscles? 

4. How do skeletal muscles produce motions ? 

5. Explain the apparatus you have made for Experi¬ 
ment 18. 

6. What is beefsteak ? 

7. What is the use of a tendon ? 

8. Where are the muscles that move the fingers ? 

9. Where is the biceps ? What is its use ? 

10. What makes a muscle contract ? 

11. What are the two kinds of muscle? 

12. How do they differ in their use ? 

13. What is the structure of a muscle? 

14. How do muscles get their food? 

15. Find 12 muscles in the face and neck (Fig. 59), 
and tell what they do. 

16. How can muscle be developed? 

17. What kinds of exercises are good for muscles ? 

18. What is the advantage of a trained muscle? 

19. How does alcohol affect muscle? 

20. Give five reasons why an employer would rather 
hire a man who does not drink alcohol. 


186 SECOND BOOK OF PHYSIOLOGY 


21. Why does a railroad company object to a drinker? 

22. Why are the boys who enter athletic contests re¬ 
quired to abstain from alcohol and tobacco ? 

2 Give some good reasons for not using tobacco. 


CHAPTER IX 


THE SKIN 

The use of the skin.—The skin covers 
the whole outer surface of the body. It is 
tough, elastic, and pliable. 

The hair, nails, and teeth are only skin that 
has been much changed. 

The skin is very useful. 

(1) It protects the body in many ways, as 
from poisons, diseases, bites, cuts, scratches, 
and so on. 

(2) Its many nerves send word to the brain 
at once whenever the body is touched at any 
point. 

(3) It contains many glands that help to 
take poisonous matter out of the blood. 

(4) The water of the sweat is poured out 
on the surface of the skin and there evapo¬ 
rates. This cools the body when it is too 
warm. 

187 


188 SECOND BOOK OF PHYSIOLOGY 


The two layers of skin. —The skin is 
formed of two layers. The outer one is called 
the epidermis , and just below it is the true 
skin . 



Fig. 6i.— Cross-section of skin, <?, epidermis; c, layer which com 
tains the coloring matter; p , papillae ; g, g , g , sweat-glands ; r , root 
of hair; o , oil-glands ; s, s, s , sweat-pores ; f, fat cells. 


The epidermis is in most places very thin 
and nearly transparent. The color of the 
blood shows through it and gives the skin a 
pink appearance. The cells of the epidermis 
are flat and dried. They are not alive like 








THE SKIN 


189 


other cells, but are cemented together edge to 
edge, as shown in Fig. 62. Several layers like 
this form the tough epidermis. 

Growth of the epidermis. —The outside 
cells of the epidermis are constantly falling 
off or are rubbed .off by the 
clothes and by bathing. Other 
cells are as constantly being 
added to it on its under side. 

If any part be constantly 
rubbed or pressed for a long 
time, the cells will be added in 
great numbers there. This is Fig - 62 -— Cellsof the 

0 epidermis. 

what makes the skin in the hand 
of a workman very hard and thick. The skin 
is trying to protect the delicate parts beneath 
it. Corns are produced in the same way by 
tight shoes. 

Color of the skin. —In the lowest layers 
of the epidermis are placed the little grains 
of matter that give the color to the skin. 
These make some people black, others yellow, 
and others red. In a white skin there is very 



1 9 o SECOND BOOK OF PHYSIOLOGY 

little coloring matter. The sunlight may 
change the color of these grains and “tan” 
the skin. When the grains are more numer¬ 
ous in spots they are called freckles. 

The true skin. —In Fig. 61 it can be seen 
that the true skin contains sweat-glands, roots 
of hairs, oil-glands, fat, blood-vessels, and is 
covered with numerous ridges, called papillae, 
just under the epidermis. 

The chief purpose of the epidermis is to 
protect the parts beneath it; but the true skin 
has important work to do. 

The papillae. —Some of the papillae con¬ 
tain only blood-vessels, and others contain the 
ends of the nerves of touch. The slightest 
touch on any part of the body is reported to 
the mind by these nerves. They are placed 
very close together on the ends of the fingers 
and on the palms, and they are there arranged 
in rows that can be seen with the naked eye. 

The fat cells. —Numerous fat cells are 
found beneath the layer of papillae. When 


THE SKIN 


191 

they are in abundance, they make the skin 
smooth and give the face and hands a plump 
appearance. When the fat is wanting, there 
is more skin than is needed, and it then lies in 
folds or wrinkles. 

Sweat-glands. —A number of sweat-glands 
are shown in Fig. 61. They are long tubes 



Fig. 63.—Sweat-pores in palm of the hand. 


coiled up at one end, while the other end opens 
on the surface of the skin. These openings 
are the sweat-pores . They are most numerous 
on the palms and soles. Fig. 63 is a magni¬ 
fied appearance of the rows of papillae and 


192 second book of physiology 

the pores from a spot on the palm of the 
hand. 

Perspiration. —The blood circulates 
through capillaries close about the sweat- 
glands, and the cells of the gland take from it 
a great deal of water and several impurities. 

This is the sweat which then passes up 
through the long ducts and oozes out on the 
surface of the epidermis. This is going on at 
all times and is called perspiration . 

When the sweat dries up as fast as it comes 
out, we may not notice it; but at other times 
it comes so rapidly that drops of sweat stand 
on the surface of the skin. About one quart 
of water is perspired by the body in one day. 

Experiment 19.—Thrust the hand into a 
cold fruit jar or wide-mouthed bottle and hold 
it upside down. Let a cold wind blow on the 
bottle. Drops of water will collect on the inner 
surface of the glass. The water came from 
the pores of the skin and was condensed by 
the cold. 


THE SKIN 


*93 


How sweat regulates the heat of the 
body. —The temperature of the body must 
be about the same all the time. It must never 
get much warmer or cooler than 98° Fahren¬ 
heit. 

The combustion of food in the body is all 
the time producing heat. Why, then, does 
the body not become overheated ? 

The air is nearly always cooler than the 
body, so that every time we breathe we let out 
some of the heat in the body. A great deal 
of heat also escapes from the body, just as it 
escapes from a hot stove to the air in a room. 
But when the day is very warm, or when we 
work or exercise very hard, the body will be 
heated faster than it is cooled in these ways. 
Then is when the sweat comes out to help in 
cooling the body. 

A liquid cannot turn to a gas or vapor un¬ 
less it can get heat. When the water in the 
sweat turns to a vapor, it must have heat, and 
it gets it from the warm body. It is not the 
sweat, but the drying up of the sweat, that 
makes us cool. Fanning cools the face be- 


13 


i 9 4 SECOND BOOK OF PHYSIOLOGY 

cause it dries the sweat faster. Fanning would 
do no good if the skin were perfectly dry. 
That is why a warm wind feels cool if the skin 
is wet. 

Experiment 20. —Place one of your hands 
in warm water and then hold it near a register 
in the draft of hot air. The air will feel cool. 
The hot air dried the water so rapidly that the 
hand was cooled instead of warmed. 

Experiment 21. —Fan the dry thermom¬ 
eter in your room, and you will find that the 
mercury will not fall, however hard you may 
fan. 

Now wet the bulb with some water that has 
been in the room and has the same tempera¬ 
ture as the air, or a little warmer. Jslow fan 
again, and the mercury will fall. The cooling 
is caused by the rapid evaporation of the 
water. The cooling is still greater if alcohol 
or gasoline is used instead of water. 

Experiment 22. —Raise the window a 
little. Wet one finger in the mouth and hold 


THE SKIN 


*95 


it at the opening. If the inner side of the 
finger feels cooler, the air must be going out. 
If the outer side, the air must be coming into 
the room. 

In a similar way you can tell which way the 
wind is blowing when you are out of doors.. 

How clothing keeps the body warm.— 

Heat is all the time escaping from the body 
into the air. When we wear heavy clothes, 
we keep the heat in, and also check the evapo¬ 
ration of the moisture on the skin. Clothes 
do not warm the body. They only keep it 
from getting cold. In hot summer days we 
wear very light clothing, so the heat can 
escape. 

Hair. —Hair grows on nearly all parts of 
the surface of the body. It is thick on the 
head, and is useful there to protect the head 
from heat and cold, and from accidental in¬ 
juries. The eyebrows and eyelashes help to 
protect the eye, and the hairs in the nose and 
ears are useful there as guards. 


196 SECOND BOOK OF PHYSIOLOGY 

Hairs are a part of the epidermis. They are 
composed of cells, which are formed at the 
bottom of the root. The 
new cells push the old ones 
ahead of them, and in that 
way the hair grows. 

At the side of the hair, 
as shown in Fig. 64, are oil- 
glands. They keep the hair 
oiled and glossy. The oil 
also makes the epidermis 
soft and pliable, so that it 
may not crack and become 
chafed. 

The nails. —The nails are also a part of 
the epidermis. The root of the nail is the back 
part of it where it is attached to the true skin. 
There new cells are added which push the 
nail forward and make it grow. The under 
side of the nail is attached to the true skin, 
which shows through the transparent nail and 
makes it look pink. 

The free edge of the nail is very useful in 
many things which we have to do. 



Fig. 64.—The root of 
a hair. 


THE SKIN 


197 


The skin is fastened so tightly to the back 
and sides of the nail that it may be torn by the 
nail’s growth. This causes the “ hang-nail,” 
which may become very 
sore and painful. It 
may be avoided by push¬ 
ing the skin back once 
in a while. 

The free edges often F,G ' ^ se f ion of the 

0 end of a finger. 

become ragged and 

filled with dirt. They must have proper care 
two or three times a day. A stiff nail-brush, 
with soap and water, is good for cleaning the 
nails, and a sharp knife may be used to trim 
them when necessary. Dirty nails show care¬ 
less habits. 

Bathing. —Frequent bathing is necessary 
to remove the grease, dust, and dirt that rap¬ 
idly gather on the surface of the body. One 
should bathe and keep his body clean if for 
nothing else than to make himself agreeable to 
other people. But bathing is also necessary 
for the sake of good health. If many of the 






198 SECOND BOOK OF PHYSIOLOGY 

pores are stopped, the perspiration is checked. 
Then the skin cannot throw out the waste and 
impurities as it should do. A person would 
become very sick if his sweat-glands should 
cease their work, or if all the pores were 
tightly stopped. Often when one feels inac¬ 
tive or is catching a cold, it is a good plan to 
take some vigorous exercise and keep it up 
till the skin is wet with sweat. 

The impurities that cause the trouble may 
in that way be thrown off. 

The experiment has been tried of covering 
an animal all over with thick varnish so that all 
pores were closed. The animal grew sick 
and died. 

These things show that it is necessary to 
keep the skin clean and in a healthy condition. 

The body should be bathed with water and 
soap about once a week. In hot weather it 
may be necessary to bathe more frequently, 
and in cold weather not so often. 

It is very convenient if one can have a bath¬ 
room provided with a bath-tub where he can 
turn on hot or cold water. But a good bath 


THE SKIN 


1 99 


can be had without these things. A basin of 
soft, warm water and a sponge or wash-rag 
with some good soap and dry towels are ail 
that is needed for a thorough bath. These are 
within the reach of every one, and so there can 
be no excuse for not having a clean body. 

Frequent changes of underclothing is also 
quite as necessary as the bath. Even when 
the clothing looks clean, it may be full of filthy 
matter which it has absorbed from the skin. 

QUESTIONS. 

1. Give four uses of the skin. 

2. What are the two layers of the skin ? 

3. What is epidermis, and how does it grow? 

4. What is a corn ? 

5. Could one have corns on his fingers? 

6. Why is the skin of a negro black ? 

7. What is an albino? (Look in the dictionary.) 

8. What does the true skin contain? 

9. What is the use of the papillae ? 

10. What causes wrinkles in the skin? 

11. Describe a sweat-gland. 

12. What is perspiration ? 

13. How much water may be perspired in one day? 

14. How can you show that water is escaping from 


200 SECOND BOOK OF PHYSIOLOGY 


the hand even when no sweat can be seen ? Have you 
tried it? 

15. What is the proper temperature of the body? 

16. Name several ways by which heat escapes from 
the body. 

17. How can sweat cool the body? 

18. Why does fanning cool the body? 

19. Can a dry thermometer be cooled by fanning it? 
Have you tried it? 

20. How can you tell which way the wind is blowing? 

21. Does clothing warm the body? What is the use 
of heavy clothing ? 

22. Of what use is hair? 

23. How does a hair grow ? 

24. What makes the hair oily? 

25. How does a nail grow? 

26. What care do nails need? 

27. Give some good reasons for bathing. 

28. Why should underclothes be frequently changed? 


CHAPTER X 


EXCRETION. 

What excretion is.—Excretion is the 
process by which waste and impurities are 
removed from the cells and thrown out of the 
body. 

When wood or coal is burned in a stove, 
some waste is always formed, which must be 
carried away so that fresh coal or wood may 
be burned. The smoke and carbon dioxide 
are waste which goes up the chimney, and the 
ashes are collected in the ash-pan. 

When food is burned in the cells of the 
body, waste is always formed, and must be 
carried away or the life of the cell would 
soon end. 

Lymph.—Lymph is the fluid which sur¬ 
rounds the cells. It is like blood, except that 
it contains no red corpuscles. When the 
blood is in the capillaries, the thin liquid fluid 


201 


202 


SECOND BOOK OF PHYSIOLOGY 


will ooze into the lymph, and the cell is then 
bathed in the food which it needs. The red 
corpuscles only give up their oxygen, and then 
pass on in the current of blood; but the white 
corpuscles can pass through the walls of the 
capillaries and move about the cells. 

When the cell burns up some of its food, 
that is, makes it unite with the oxygen, waste 



Fig. 66.—Illustration of a cell bathed in lymph. White corpuscles 
are shown in lymph. 

substances are produced which must be car¬ 
ried away. One very common kind of waste 
is carbon dioxide. This passes out into the 
blood and is carried back to the heart. So 
the same stream of blood that brought the 



EXCRETION 


203 


food and oxygen also carries away one of the 
wastes. 

But other waste substances are also pro¬ 
duced, and they soon make the lymph about 
the cells very impure. So there must be 
some way of draining off the old lymph. 
This is done by millions of fine tubes called 
lymphatics. They are much like veins and 
have many valves. They carry impure lymph, 
while veins carry impure blood. 

The fine lymphatics unite and form larger 
tubes, which pour the impure lymph into large 
veins in the neck, whence it soon gets back to 
the heart. 

The thoracic duct which we described in 
digestion is the tube which collects the 
larger part of the lymph. The lacteals in the 
villi of the small intestines are a part of this 
system of lymphatics. 

So the waste produced by the cells is 
carried away by the veins and the lymphatics. 

How the impurities are taken out of 
the blood.—Impurities are brought to the 


204 SECOND BOOK OF PHYSIOLOGY 

heart by both the veins and the lymphatics. 
Unless they are taken out of the blood, it will 
soon become crowded with waste and poisons. 
So we find that several organs are at work 
purifying the blood. The chief ones are the 
lungs , liver, kidneys , and skin. 

We have already explained that all the 
blood is brought back to the right auricle of 
the heart. Thence it goes to the right ven¬ 
tricle, which sends it to the lungs. While it is 
passing through the lungs, the carbon dioxide 
escapes from the blood into the air-sacs and is 
then breathed out. The lungs excrete carbon 
dioxide and small amounts of other impuri¬ 
ties. 

We have already described the liver and 
the work it does. It is very useful in several 
ways. One of its important uses is to purify 
the blood. It gathers up the bile and pours 
it into the small intestine. Bile is not wanted 
in the blood, but it is useful in digestion. 

The liver also excretes other impurities 
which would soon poison the cells if they were 
left in the blood. 


EXCRETION 


205 


The kidneys. —The two kidneys are 
located in the abdomen, one on each side of 
the spinal column in the small of the back. 



Fig. 67. —Cross-section of kidney. C, C, cortex ; M, pyramids 
of Malpighi; Z, Z, medulla ; P, pelvis; A, artery ; V> vein ; U y 
ureter. 

Each kidney is about four inches long and 
shaped like a bean. 

An artery runs to each kidney and carries 





206 SECOND BOOK OF PHYSIOLOGY 


a large amount of blood to them, and a vein 
from each carries the blood away. The middle 
tube, shown in Fig. 67, carries off the water 
and impurities which the kidneys gather out 
of the blood. 

The chief work of the kidneys is to excrete 
urea. Urea is a waste which comes from the 
use of proteid food. This kind of food is very 
important; and it is natural that a small quan¬ 
tity of urea should be present in the blood at 
all times; but the kidneys must work day 
and night taking urea out of the blood or the 
body would soon be poisoned. A man would 
probably not live more than one day if his 
kidneys would cease to work. 

The skin assists the kidneys, for the sweat- 
glands not only pour out water, but also some 
urea and several salts. 

Effect of alcohol on the organs of ex¬ 
cretion.—We have already explained how al¬ 
cohol injures the lungs and the liver. Its effect 
on the kidneys is equally bad. It often changes 
part of the kidney-cells to fat-cells. Fat-cells, 


EXCRETION 


207 


we have learned, can do no work. So there 
will be fewer cells to do the work of the kid¬ 
neys. At the same time alcohol causes more 
impurities in the body and weakens the organs 
that try to excrete them. The result is that 
either the organs are overworked or the blood 
will be allowed to pass through without being 
purified. 

Alcohol is the cause of a great deal of kid¬ 
ney trouble, and many -persons who drink a 
great deal of alcohol have some trouble of that 
kind. When the kidneys break down, the dis¬ 
ease is known as Bright’s disease. The skin 
will then excrete more urea than usual, but it 
cannot do all the work of the kidneys, and so 
the blood soon fills with poison and death is 
almost sure to follow. 

There is no organ of the body that is not 
weakened by the continued use of alcohol. 

QUESTIONS. 

1. What is meant by excretion ? 

2. What waste is formed when coal is burned ? 

3. What is lymph ? 

4. How does lymph differ from blood ? 


208 SECOND BOOK OF PHYSIOLOGY 


5. How is the carbon dioxide removed from the 
lymph ? 

6. How is the impure lymph drained away from the 
cell? 

7. How are lymphatics like veins? 

8. Where is the impure lymph taken ? 

9. Name four important organs that take impurities 
out of the blood. 

10. What part do the lungs do? 

11. What part does the liver do ? 

12. Describe the kidneys. 

13. What is the chief work of the kidneys? 

14. What is urea? 

15. What does the skin excrete? 

16. How does alcohol injure the kidneys? 


CHAPTER XI 


THE NERVOUS SYSTEM 

Parts of the nervous system.—The ner¬ 
vous system is composed of five important 
parts, (i) One large nerve-centre—the brain. 
(2) A long nerve-centre in the spinal column 
—the spinal cord. (3) Many small nerve-cen¬ 
tres—the ganglia—found at many places in 
the body. (4) The nerves which run from the 
nerve-centres out to every part of the body. 
(5) Nerve endings, as where a nerve ends in a 
muscle or gland. 

The nerve-cell.—The nervous system is 
composed of cells just as other parts of the 
body are, but they are quite different in shape. 
A nerve-cell in the spinal cord may have to 
control a cell of muscle in the hand. It must 
then be able to reach all the way from the cord 
to the hand. So we find that most nerve-cells 
have long branches running out from them. 

14 ' 209 


2io SECOND BOOK OF PHYSIOLOGY 



V 

Fig. 68.—A nerve-cell, m, body of cell; n , nucleus; t, short 
branches ; a, long branch which runs to e, and is covered most of the 
way by a white sheath. 







THE NERVOUS SYSTEM 


2 11 


As a rule, there is only one very long branch 
and a number of small ones. In Fig. 68 you 
can see the parts of a nerve-cell. It has a 
body and a nucleus, and is composed of the 
same kind of material as the other cells ; but 
it is different in having the long branch that 
may reach out two or three feet from the 
body of the cell to another cell over which it 
has control. When we use any of the skeletal 
muscles, we must first send an order out on 
the long branches of the nerve-cells to the 
muscle-cells. 

When a large number of these cells are 
clustered together they are called a nerve- 
centre, and a number of the long branches 
bound together are called a nerve. 

All the nerve-centres are in the brain, the 
spinal cord, and the ganglia. 

Everything we do and every movement we 
make starts in the nerve-centres. 

The brain.—The brain is the most im¬ 
portant part of the human body. It is very 
delicate and easily injured, and so we find it 


2i2 SECOND BOOK OF PHYSIOLOGY 

well protected. It is enclosed in a strong, bony 
box called the cranium. The flat bones of 
the cranium are quite thick and strong, and 
will bear a heavy stroke or pressure without 
breaking. 



Fig. 69.—Nerve-cells from the brain. 


The brain of man is larger in proportion to 
the size of his body than that of any other 
animal. The brain of man is not only large, 
but it is also fine in quality ; so that man is the 
most intelligent of all animals. 










THE NERVOUS SYSTEM 


213 


The average weight of the human brain is 
about three pounds. Some weigh as much 
as four pounds or more, but the most intelli¬ 
gent man does not always have the largest 
brain. An average sized brain of good 
quality is better than a large brain of poor 
quality. 

The brain is composed of a great number 
of cells similar to the one shown in Fig. 68. 
Several are shown in Fig. 69. A large cluster 
of cell-bodies have a grayish appearance, and 
so they are called the gray matter of the brain. 
The long branches covered with the white 
sheath are called the white matter. 

The brain is divided into four important 
parts, called the cerebrum, cerebellum, medulla 
oblongata, and th ^ pons. 

The Cerebrum.—As may be seen in Fig. 
70, the cerebrum is much the largest part of 
the brain. It occupies the whole of the cra¬ 
nium above the ears. Its weight is about two- 
thirds of the weight of the whole brain. You 
can see only the right side of the brain in 


214 


SECOND BOOK OF PHYSIOLOGY 


Fig. 70. The brain is double, and the two 
sides are just alike. The two halves of 
the cerebrum are called the right and left 
hemispheres. They are connected by fibres 
which run across from one side to the other. 

The surface of the cerebrum lies in folds 



Fig. 70.—The parts of the brain. 

called convolutions. These greatly increase 
the area of the surface. 

The gray matter of the cerebrum is on the 
outside. It varies from about one-sixth to 
one-twelfth of an inch in thickness and runs 
in and out on all the convolutions, as shown 


THE NERVOUS SYSTEM 


2^5 


in Fig. 71. The gray matter is the most im¬ 
portant part of the cerebrum, for it is made 
up of the bodies of the nerve-cells. 



Fig. 71.—Section of cerebrum showing gray matter on outside. 


Under the gray is the white matter, which 
is composed of bundles of white nerve-fibres 
running down from the cells of the gray 
matter. 

The cerebellum.—The cerebellum is the 
small brain in the back part of the head, below 
the cerebrum. It is composed of the gray and 
white matter, and is divided into two equal 
halves, which are connected to each other by 
many fibres through the pons. 


216 SECOND BOOK OF PHYSIOLOGY 


The medulla oblongata.—The medulla 
oblongata is the part of the upper end of the 
spinal cord that is inside of the skull. 

This is a very important part of the brain, as 
we will show later. It is also divided into two 
equal parts and contains both white and gray 
matter. The nerve-fibres from the brain pass 
over to the other side in the medulla. So the 
left hemisphere of the cerebrum sends nerves 
to the right side of the body, and the right 
hemisphere to the left side. 

Nerves.—Nerves are the paths along which 
messages are sent out from the nerve-centres 
to all parts of the body, and by which mes¬ 
sages are received from all parts of the body. 

They are smooth, white, glistening cords, 
being a bundle of the very fine nerve-fibres 
which are the long branches from the cells. 
Nerves are of many different sizes. Some are 
so small that they cannot be seen with the 
naked eye. The largest one is the great 
sciatic nerve which runs down the back part 
of the thigh. It is a broad band about two-thirds 


THE NERVOUS SYSTEM 


217 


of an inch across. Branches from it are dis¬ 
tributed to the muscles of the legs and feet. 

Two kinds of nerve-fibres are bound up in 
the same nerve. One kind is called efferent. 
They carry messages out from the nerve- 



Fig. 72.—Cross-section of a nerve, showing numerous nerve-fibres 
bound together. 

centres. The other kind is called afferent. 
They carry messages into the nerve-centres. 

The efferent nerves are called motor because 
we use them in moving the muscles. The 
afferent nerves are called sensory because we 
use them in receiving sensations. 

Twelve pairs of nerves run from the brain 
to the various parts of the face, head, and 
body. They are called cranial nerves. 


218 SECOND BOOK OF PHYSIOLOGY 


Thirty-one pairs of nerves run from the 
spinal cord out over the greater part of the 
body. They are called spinal nerves. 

The spinal cord.—We have already ex¬ 
plained that the holes through the vertebrae, 
when placed one above the other, form a 



Fig. 73.—Cross-section of the spinal cord. W, white matter ; G, 
gray matter ; A, front part. 

long tube running through the spinal column. 
Within this is the spinal cord . 

The cord of the adult is about 18 inches 
long and about one-half an inch in diameter. 
It, like the brain, is very well protected from 
injury. 


THE NERVOUS SYSTEM 


219 


A cross-section of the cord, Fig. 73, shows 
that it is composed of gray and white matter, 
but the white is on the outside and the gray 
inside. 

A deep groove, before and behind, nearly 
divides the cord into two equal halves. A 
narrow isthmus connects one side with the 
other. 

The white matter is composed of a great 
number of nerve-fibres running up and down 
the cord. The gray matter is composed of 
nerve-cells. The appearance of the gray 
matter in the section of the cord is something 
like the letter H. 

Spinal nerves.—Numerous nerves branch 
off from the sides of the spinal cord. They 
are called spinal nerves , and there are in all 31 
pairs of them,—that is, 31 nerves from each 
side. 

In Fig. 74 you can see how they start from 
the cord, though only one pair is shown in this 
figure. 

Those that start on the front side of the 


220 SECOND BOOK OF PHYSIOLOGY 


cord, on both sides of the deep groove, are 
motor nerves. We use them when we wish 
to move the hand, feet, or other parts of the 
body that are not controlled by cranial nerves. 



Fig. 74.—A piece of spinal cord. A , A, anterior, motor, or 
efferent nerve-roots ; P , P, posterior, sensory, or afferent nerve-roots ; 
G f Gy ganglia on posterior roots ; S f S , beginning of spinal nerves. 

Those that start from the back part of the 
cord are sensory nerves. We use them, for 
example, when we pass our fingers over any 
object to see whether it is rough or smooth. 
If the skin is touched, scratched, or burned, 
the sensory nerves report the fact to the 
brain. 

These two kinds of nerves soon unite into 
one bundle and pass out between the verte¬ 
brae of the spinal column. 

Nerve endings. —The motor nerves run 
out to all cells where any kind of action is 
produced. Fine nerve-fibres run to each cell 



THE NERVOUS SYSTEM 


221 


of a muscle, gland, or other part of the body 
under control of the nerve-centres. The 
nerve-cells not only cause all the action in the 
other cells, but they also regulate the action 
so it will not be too fast or too slow. Such 
nerve-fibres end in the cells which they 
operate. 

The sensory nerves often have very com¬ 
plex organs at their ends, so that a very slight 
disturbance there will be reported to the brain. 
The eye and ear are such organs, and there 
are also organs of touch, taste, and smell, 
making the five special sense organs which are 
described in the last chapter. 

Sympathetic nerves.—Most of the nerves 
that we have described are operated by the 
great nerve-centres in the brain and spinal 
cord. But in addition to these there are also 
many other nerves which are not under the 
direction of the will. They do their work 
whenever it is necessary, and we may know 
nothing about it. The beating of the heart, 
breathing, digestion of food, and so on, are all 


222 SECOND BOOK OF PHYSIOLOGY 

caused and regulated by sympathetic nerves. 
These nerves are called sympathetic because 
they make the organs they control work in 
sympathy with each other. When the muscles 
are made to work they need more blood. The 
arteries get larger, the heart beats faster, 
breathing is quickened, and the stomach tries 
to supply more food. This is what is meant 
by working in sympathy. Each organ is de¬ 
pendent on the others, and there must be 
some arrangement of this kind for the good 
of all. 

What the cerebrum does.—The size, 
shape, and quality of the human cerebrum is 
the chief difference between the brain of a man 
and that of a horse, dog, or monkey. The 
human cerebrum is not only larger in bulk, but 
it has more and deeper convolutions on its 
surface, and so a greater number of cells in 
the gray matter. 

All mental operations are performed in the 
cerebrum. It is there that we think, study, 
solve problems, and commit to memory. 


THE NERVOUS SYSTEM 


223 


It is in the cerebrum that we make up our 
minds to do anything, that is, use our will 
power. 

The cerebrum is the centre of all sensation. 
We cannot know, for example, that the foot 
has been touched until a message has travelled 
all the way from the foot to the head and has 
made an impression on the cerebrum. 

A division of labor among the cells of 
the cerebrum.—The act of thinking is per¬ 
formed by all the cells of the cerebrum acting 
together, but certain groups of cells have dif¬ 
ferent work to do both in sending out orders 
and in receiving sensations. Many experi¬ 
ments have been made to find out just what 
part of the brain moves the fingers, toes, legs, 
arms, and so on. Also to find what part re¬ 
ceives sensations from the eyes, ears, tongue, 
nose, skin, and so on. Many of these spots 
are mapped out and are located as shown in 

Fig. 75 - 

The areas that cause motion are called 
motor areas , and those that receive sensations 


224 SECOND BOOK OF PHYSIOLOGY 

are called sensory areas . If any of these 
motor areas are injured, the part of the body 
that it controls will be paralyzed and helpless. 
If the whole right hemisphere of the cerebrum 



Fig. 75.—The motor and sensory areas of the cerebrum. (The 
front is on your left). 


should be injured, the whole left half of the 
body would be helpless and without feeling. 
If any sensory area should be injured, the part 
of the body from which sensory nerves come 
to it would be numb and without any feeling. 
The part could then be cut or burned without 
any pain. 






THE NERVOUS SYSTEM 


225 

Use of the cerebellum.—The chief use 
of the cerebellum seems to be to balance the 
body. When the cerebellum is injured, the 
cerebrum can still cause the muscles to con¬ 
tract, but their action will be uncertain and 
irregular. When such a person attempts to 
walk he will stagger and sway from side to side. 
He cannot even stand without some support. 

From such experiments, it appears that the 
cerebellum has the power of regulating the 
contraction of muscles and making them work 
together in just the right way to produce the 
motion we wish. A man can strike just as 
hard without a cerebellum, but he cannot be 
sure of hitting what he strikes at. 

Use of the medulla and cord.—The 
white matter of the medulla and cord is com¬ 
posed of numerous nerve-fibres which run to 
and from the brain. They carry messages to 
and from the nerve-centres, chiefly the great 
nerve-centre, the cerebrum ; but the gray mat¬ 
ter in the medulla and cord are also nerve-cen¬ 
tres of great importance. An injury to the 
*5 


226 SECOND BOOK OF PHYSIOLOGY 


medulla will cause death more quickly and 
surely than a similar injury to any other part of 
the body. A bullet may pass through the cere¬ 
brum without causing death, but death follows 
instantly when any violent injury is done to the 
medulla. This is because the gray matter in the 
medulla operates several organs upon whose 
action life depends. Breathing is caused by a 
centre in the medulla. If this centre is injured, 
breathing will cease at once. It is even stronger 
than the cerebrum, for, although we may stop 
breathing for a time, it will soon begin in spite 
of any effort of the will. 

The medulla also regulates the beating of 
the heart, making the beats regular and of the 
proper frequency to supply the blood when it 
is needed. Sometimes, when the medulla is 
injured by the use of tobacco or alcohol, the 
heart will flutter and be irregular in action. 

Other centres in the medulla will regulate 
the size of the arteries, cause coughing, sneez¬ 
ing, or vomiting. 

Such work of a nerve-centre is called reflex 
action. 


THE NERVOUS SYSTEM 227 

Reflex action. —When a sensory nerve 
brings a message to a nerve-centre in the 
medulla or cord, and the nerve-cells in that 
centre at once send back an order to a muscle, 
the action is called reflex. 

The medulla and the cord are the chief 
centres of this kind of action. In Fig. 76 can 


p 



PlG. 76.—Diagram showing the origin and relation of afferent and efferent 
nerves. S, skin ; G, ganglion ; P, posterior horns; M, muscle; af afferent 
nene; ef efferent nerve ; A , anterior horns. 


be seen the path along which a message travels 
in case of a reflex action. If the hand be acci¬ 
dentally pricked with a pin, or be touched 
with a hot iron, the sensory nerve will at once 
report it to the gray matter in the cord, and 
me cells there will at once send back an order 
on the motor nerves to the muscles there to 
pull the hand away. 




228 SECOND BOOK OF PHYSIOLOGY 

It is not necessary to wait for an order 
from the cerebrum, though it may become 
conscious that the hand has been pricked or 
burned. 

If the spinal cord should be broken in two, 
the cerebrum could not move the legs ; but if 
the foot should be tickled, the legs would move 
and draw the feet away. This would be done 
by reflex action from the lower end of the 
cord. 

In most cases of reflex action the cerebrum 
knows nothing about it, and may be entirely 
absorbed in other matters. 

Advantage of reflex action. —If the cere¬ 
brum had to give close attention to every little 
thing we have to do, it would have no time 
to study, read, write, or think. As it is, the 
reflex centres will look after most of the details 
of life after one has grown up. 

Education of the reflex centres. —It is 

possible to educate many reflex centres so 
that actions which were at first difficult to do 
may become easy. 


THE NERVOUS SYSTEM 


229 


Walking is very hard for a child because he 
must think of every step, but after many trials 
it becomes a reflex act. He can then walk 
and at the same time think about something 
else. 

It is difficult at first to make the letters 
used in writing, but after many trials one can 
dash off the words without thinking of how 
he makes them. Some always write slowly 
and poorly because they have not practised 
enough to make good writing a reflex act. 

It is the same way in learning to ride a 
bicycle or play on a musical instrument. The 
lacing and tying of shoe-strings and other little 
matters of that kind become reflex acts that 
require no attention of the mind. 

It is the duty of every young person to 
practise doing things that are worth doing 
until he can do them well even when he is 
not trying. 

Habit. —After one has learned to do any¬ 
thing in a certain way, he will be inclined to 
always do it that way. It is then said to be a 


2 3 o SECOND BOOK OF PHYSIOLOGY 


habit with him. Several repetitions of an act 
in the same way will soon form a habit. 

One who goes “down town” after supper 
for a number of times soon finds that he has 
a strong desire to go again whenever supper 
is over. 

One who has learned to tip his hat on 
speaking will do so without thinking that he 
does it. 

Habits may be good or bad * After a time 
they become fixed, and are then very hard to 
change. A good habit is one which leads us 
to do the right thing even when we do not try. 

A bad habit is almost sure to make us do 
the wrong thing unless we are constantly on 
our guard. 

If boys and girls knew how much every man 
or woman is a creature of the habits they form 
in early life, they would be very careful to 
form good ones. 

Every one should be ruled largely by habits, 
but they must be good ones. 

Habits are most easily learned in youth, 
and after one is twenty-five or thirty years of 


THE NERVOUS SYSTEM 


231 


age his habits are for the most part fixed. 
If they are all good, he is very fortunate for 
life. If they are bad, he will find it very diffi¬ 
cult to change them. Even if he does seem 
to get rid of a bad habit, it will break out in 
spite of all he can do. 

A young man who has formed good habits 
in speech, writing, conversation, walking, dili¬ 
gence, punctuality, politeness, manners, mo¬ 
rality, and so on, has a great advantage over 
one who has been careless in these matters, 
and so has bad habits. 

Food of the brain. —No part of the body 
can do any work unless it can get food and 
oxygen, just as an engine can do no work 
unless it can get coal and air. When the 
brain works, it must be supplied with good 
blood if it is to do good work. A large artery 
runs up along each side of the neck and car¬ 
ries blood to the cells of the brain. Good, 
nourishing food and pure air are necessary to 
make good blood, and so they are necessary 
to good thinking. About one-eighth of the 


232 SECOND BOOK OF PHYSIOLOGY 

blood in the body is supplied to the brain, and 
if the flow of blood should cease, one would 
become unconscious at once. 

Fatigue of the brain. —Brain-cells become 
tired just like cells of muscle. Both kinds of 
cells get from the blood a certain amount of 



Fig. 77. — A , a cell stored with energy-yielding material; B, same 
cell fatigued after a period of work. 

energy, that is, ability to do work. When 
the energy is used up, we say the brain or 
muscle is tired. When the coal in a steam- 
engine is nearly all burned and the engine 
begins to run more slowly, we may say that 
the engine is tired. When we give it more 
coal, it is ready to do hard work again. In 
the same way the brain and muscle become 


THE NERVOUS SYSTEM 


2 33 


fatigued or tired because their store of food 
has been used up ; but if they are allowed to 
rest until they can be supplied with more food, 
they will be ready to go to work again. 

In Fig. 77 you can see a cell that is well 
supplied with food. It is round and plump. 
Beside it is shown the same cell after it has 
been at work and has become tired. It is 
shrunken because its store of food is ex¬ 
hausted. When it is stored up again it will 
be ready for more work. So each cell is like 
a little engine, and can do work only when it 
is supplied with energy. 

Sleep.—The body can get complete rest 
only when it is asleep. One can get partial 
rest while he is awake by simply stopping his 
work ; but several hours of sleep are needed 
every night that the cells may become stored 
with energy needed for the work of the day. 
This is especially true of nerve-cells, which 
seldom rest except in sleep. 

The brain thrives on hard mental work. 
Like the muscle, it must have exercise or it 


234 SECOND BOOK OF PHYSIOLOGY 

will be weak and grow still weaker, but it 
must have the proper amount of rest. 

Amount of sleep needed. —We cannot 
give any rule as to just how long one should 
sleep, but when he gets awake he should feel 
full of energy and ready for hard work of any 
kind. About eight hours of sleep are needed 
every night. Most young people get too little 
sleep, and then try to do a day’s work without 
enough of energy to last them through the 
day. Such persons make only a sleepy and 
half-hearted effort in their studies, and do 
poorly any work they attempt. 

No one will ever be hurt by study if he gets 
the right amount of sleep. The harm is done 
when we try to force the brain to work when 
the cells are already fatigued. 

The various parties and social gatherings 
which young people attend cause more bad 
health than any study they ever do. 

They not only lose the early part of the 
sleep needed, but, after the excitements of the 
gathering, may have only a restless sleep 


THE NERVOUS SYSTEM 


2 35 


during the remainder of the night. They get 
up feeling tired, and after a hurried breakfast, 
for which they have no appetite, hasten to 
school. In such a condition the brain cannot 
be used long in hard study without doing it 
injury. Both mind and body may break down 
under a long strain of this kind, but it results 
from lack of rest and sleep and not from 
overstudy. 

How to get to sleep. —Most young people 
in good health can go to sleep as soon as they 
go to bed. But there are many who do not 
easily go to sleep, and do not sleep soundly. 
They do not get complete rest, and so cannot 
be in perfect health. Such an one should try 
to get into the habit of sleeping soundly. 
Here are a few rules about sleeping: 

(1) Make sure that the air in the room is 
pure. Lower one or two windows from the 
top to get good ventilation. Have no fear of 
night air; it is just as good as day air. Do 
not sleep directly in a draft. 

(2) Use only enough of cover to keep you 


2 3 6 SECOND BOOK OF PHYSIOLOGY 

comfortable. Heavy covers will interfere with 
sleep and cause ill health. 

(3) When you go to bed, try to sleep at 
once. Do not attempt to read or think after 
you retire. In this way you can cultivate a 
habit of going to sleep as soon as the head 
“ strikes the pillow.” 

(4) See to it that the body is clean before 
retiring. A clean night-dress and clean bed¬ 
clothes will also greatly assist in securing 
refreshing sleep. 

Alcohol and the nervous system.—Alco¬ 
hol has a greater evil effect upon the nervous 
system than upon any other part of the body. 
The nerve-centres are very delicate, and for 
that reason the alcohol shows its bad effect 
upon them first. When the nerve-cells are 
injured, all the other cells will also suffer, 
because the nerve-cells control and regulate 
the others. For example, alcohol affects the 
cerebellum, so that it cannot properly do its 
work. This is the reason a drunken man 
cannot walk straight, but staggers. 


THE NERVOUS SYSTEM 


237 

Alcohol has a bad effect on the nerve-cells 
in the medulla, and so all the organs con¬ 
trolled by the medulla must suffer. 

Even if alcohol did injury to the nerve-cen¬ 
tres only, still, the whole body would be injured. 

Uses of alcohol.—Alcohol is very useful 
in many ways. It is good for dissolving gums 
and resins ; it is used in making varnishes and 
smokeless powder, and in other processes con¬ 
nected with the arts and sciences. It gives off 
a hot flame when burned in a lamp. In the 
arts and sciences it would not be possible to 
get along without it. These are all proper 
uses of alcohol, and it is a great advantage to 
mankind when used in any of these ways. 
But when it is used as a beverage, it has done 
and is doing a great deal of harm. 

A beverage is a drink. When people use 
alcohol as a beverage, they take it as a drink, 
either because they think it does them good, 
or because they like it, or have acquired a 
strong appetite for it and cannot resist the 
temptation to drink it. 


238 SECOND BOOK OF PHYSIOLOGY 

Alcohol as a beverage is not taken pure, 
but in such drinks as whiskey, beer, wine, 
hard cider, and so on. 

These have been used as a beverage for a 
long time ; but their terrible effects upon the 
brain and other organs of the human body 
were never so well known as now. 

Alcohol as a beverage is evil and only an evil. 

Effect of alcohol on the cerebrum.—* 

The cerebrum is the organ of thought and 
the master organ of the rest of the body. 
When alcohol gets into the body, it is soon 
carried in the blood to the cerebrum. There 
it excites the nerve-cells for a time, and some 
people get the idea that they can think better 
when they drink some alcohol. But, in fact, 
alcohol makes the mind have many false 
notions. When any one drinks even a moder¬ 
ate amount of whiskey or beer, he gets an 
idea that what he thinks or does is much better 
than it really is. After the effect of the drink 
has passed away, he may be ashamed of what 
he did under the influence of alcohol, and the 


THE NERVOUS SYSTEM 


2 39 


cerebrum will be left weaker than if it had 
received only a supply of pure blood. 

A little alcohol. —Every one abhors a 
drunkard ; but there are many who think that 
a little alcohol will do the brain no harm. A 
man may drink a little alcohol and not be 
harmed, just as he may take a little dose of 
any poison and not be harmed. But it does 
more harm than good, and always gives the 
body some extra work to do to get rid of it. 

Even if the body is able to get over it, the 
tendency of alcoholic drinks is always to do 
harm. 

Then there is also the danger that those 
who drink only a little will soon drink more and 
more, until they become drunkards. Nearly 
all drunkards began by drinking just a little. 

Alcohol and warmth. —One of the uses 
of food is to keep the body warm. This is 
done by the union of the food with the oxygen, 
as a stove is heated by the union of the coal 
and oxygen. Alcohol unites with oxygen and 


2 4 o SECOND BOOK OF PHYSIOLOGY 

produces heat. When it is taken into the 
body, some of it unites with oxygen and pro¬ 
duces heat; but at the same time it produces 
other changes which cause the body to lose 
more heat than it gains from the alcohol. 

Certain nerves regulate the size of the arte¬ 
ries. When the body is exposed to the cold 
weather, the arteries near the skin will be made 
to contract and keep the warm blood within 
the body, so the heat cannot easily get away. 

Now, alcohol will to some extent paralyze 
these nerves, and the blood will be allowed to 
flow out to the surface of the skin, where the 
heat can rapidly escape to the air. 

The red skin, blood-shot eyes, and swollen 
nose of an old drinker show that this is a fact. 

It is known that one who drinks whiskey on 
a cold day will freeze much sooner than those 
who rely only on plenty of food, good air, and 
exercise to keep them warm. 

The safe way. —The only way to be safe 
from the evil effects of alcoholic drink is to not 
use it at all. A few drinks of beer or wine may 


THE NERVOUS SYSTEM 


241 


do no harm as far as we can see ; but every 
drink, however small, makes it easier to take 
the next and the next, until a habit is formed 
and an appetite grows. Every drink has its 
effect and always tends towards excess. 

The laws of physiology are the same now 
as they always have been, and the experience 
of people in the past all teaches that the only 
safe way is to totally abstain from the use of 
alcohol as a beverage. 

Opium.—Opium is a strong narcotic poison. 
A narcotic is a substance that acts on the 
nerve-centres, making one sleepy and stupid. 

Opium is a drug that is obtained from the 
juice of the poppy plant. It is of great value 
in medicine. 

It is easy to get into the habit of eating and 
smoking opium, and the appetite for it becomes 
so strong that it is seldom possible to resist it. 

Many people in this country use opium, but 
its use is most common in China and India. 

No drug will so completely wreck both mind 
and body as opium. 

16 


242 SECOND BOOK OF PHYSIOLOGY 

Tobacco. —Tobacco is also a narcotic poi¬ 
son, and, although its use is not nearly so de¬ 
structive as that of alcohol and opium, it has 
proved a shackle to the highest success of 
many a boy and young man. 

The cells of the growing body, being already 
taxed with the work of building up new struc¬ 
tures, are less able to resist injurious sub¬ 
stances than those not having this work to do. 
Hence the notable injury to the health of the 
young caused by tobacco. 

By its deadening effect, tobacco tends to 
make its user less inclined to work, either with 
muscles or nerves. Hence it encourages habits 
of indolence and carelessness at just the time 
of life when the opposite habits should be form¬ 
ing. These are some of the ways in which it 
interferes with success in life. 

Boys in school, students in college, clerks 
in stores, or any one whose work is most of 
the time in a close room, are greatly harmed 
by the use of tobacco. The cheapness of the 
cigarette and its convenience for a short smoke 
make it the most harmful use of tobacco. 


THE NERVOUS SYSTEM 


243 


The cerebrum is injured by the use of 
tobacco in two ways. The nerve-cells there 
are directly poisoned by the nicotine, and 
other organs of the body are not able to 
furnish as pure blood for the nourishment of 
the brain. 

The effect of tobacco on the brain of boys 
in school is often very apparent. They are 
often restless and inattentive ; they are not 
able to keep their minds upon what they are 
reading; they cannot commit to memory; 
they fall behind and want to quit school. 
Tobacco is not the cause of all such failures, 
but a good scholar may easily be made a poor 
one by the use of tobacco. 

Tobacco not only harms the mind and body, 
but it makes boys careless in their habits, less 
polite, and rougher in disposition. This is 
one reason why boys that smoke are shut out 
from some of the best positions. 

Any boy who will take a sensible view of 
the whole matter will decide that it does not 
pay to learn to use tobacco. 


244 SECOND BOOK OF PHYSIOLOGY 
QUESTIONS. 

1. Name four parts of the nervous system. 

2. How do nerve-cells differ from other kinds? 

3. What is a nerve-centre ? 

4. How is the brain protected ? 

5. What does a human brain weigh? 

6. How does gray differ from white matter? 

7. Name four parts of the brain. 

8. What is the size of the cerebrum ? 

9. What are convolutions? 

10. Describe the gray matter of the cerebrum. 

11. Describe the medulla oblongata. 

12. What are nerves? 

13. How do afferent differ from efferent nerves? 

14. How many pairs of nerves are there? 

15. Describe the spinal cord. 

16. Make a drawing of a cross-section of a spinal cord, 
and describe the parts. 

17. What are the two kinds of nerve-fibres in a spinal 
nerve ? 

18. What are sympathetic nerves, and why are they so 
called ? 

19. What is the work of the cerebrum? 

20. How is the work divided among the cells of the 
cerebrum ? 

21. Find in Fig. 75 the group of cells that move the 


THE NERVOUS SYSTEM 


245 


wrist, the thumb, the ankle, the lower jaw, the eyes, 
and so on. 

22. Find the sensory regions of sight, hearing, tasting 
and feeling. 

23. In what part of the head are the sensory regions? 

24. What is the use of the medulla? 

25. What is meant by reflex action? 

26. How is reflex action an advantage to us? 

27. Name several kinds of action that are reflex. 

28. Name several actions that may be made reflex. 

29. What is a habit? 

30. How are habits formed ? 

31. Why is it important to have good habits? 

32. Why is the brain supplied with blood? 

33. How does study affect the brain ? 

34. Why is sleep needed ? 

35. How much sleep is necessary ? 

36. How is the brain injured by loss of sleep ? 

37. Give four rules for good sleeping. 

38. What is a beverage ? 

39. Name several alcoholic beverages. 

40. How does alcohol injure the cerebrum ? 

41. Why is a moderate use of alcohol harmful? 

42. Show that drinking alcohol is not a good way to 
warm the body. 

43. What is opium, and how is it used? 

44. Describe the evil effects of tobacco. 


CHAPTER XII 


THE SPECIAL SENSES. 

What the special senses are.—The sense 

of sight , hearing , feeling , tasting , and smelling 
are called the yW special senses . They are 
called special because there are special organs 
which help to make the sensation clear and 
distinct. The eye is the special organ of 
sight; the ear is the special organ of hearing ; 
the touch papillae, of feeling; the taste-buds 
on the tongue, of tasting ; and special nerve 
endings in the nose, of smelling. 

Where sensations are made.—Sensa¬ 
tions are all produced in the cerebrum, and 
never in the organ of sensation. Thus we 
have the sensation of light in the back part 
of the cerebrum, and not in the eye. The 
sensation of hearing is also in a region in the 
back part of the cerebrum, and not in the ear. 
The same is true of all sensations. Pain 

246 


", 


THE SPECIAL SENSES 247 

seems to be in the foot, hand, stomach, or 
other part of the body, but it is only in the 
cerebrum, which is also able to locate the 
cause of the pain. If the sensory nerves from 
the hand to the cerebrum were severed, the 
hand could be burned or cut without any pain. 

The advantage of the special senses.— 

All of our senses are valuable to us, but part 
of them are only general, that is, they are not 
very definite and distinct. They are such as 
the sense of pain, weight, pressure, temper¬ 
ature, hunger, thirst, fatigue, and illness. The 
sensory nerves which carry these general sen¬ 
sations have no special organs at their ends. 

The sensory nerves of the special senses 
have very delicate organs, such as the eye 
and ear, at their outer ends. By means of 
these organs a very small amount of light or 
sound, or the faintest touch on the skin, may 
cause a sensation. 

The special senses enable us to get clear 
and distinct knowledge of things outside of 
the body. 


248 SECOND BOOK OF PHYSIOLOGY 


The eye. —The eye is nearly spherical in 
shape, about one inch in diameter, and is 
placed in a bony socket on a bed of fat. It is 
covered with a tough white coat. In the front 
is the cornea. The cornea is very clear and 
bulges forward. Just under the cornea is a 
thin liquid called the aqueous humor. A little 



Fig. 78. —Cross-section of the eye. C> the cornea; A, aqueous 
humor ; I, iris ; Z, crystalline lens ; V y vitreous humor ; S, sclerotic 
coat; Ch y choroid coat; R , retina ; O, optic nerve ; Y y yellow spot. 

farther in is the iris. The iris is a beautiful 
curtain having in its centre a hole called the 
pupil. The curtain may be drawn back or 
pulled towards the centre, making the pupil 
larger or smaller when necessary. Just back 
of the pupil is the crystalline lens. Back of 


THE SPECIAL SENSES 


249 


the lens is a thick liquid called vitreous humor. 
It fills the larger part of the eyeball. The 
optic nerve enters the back part of the eye 
and spreads out into a thin net-work called 

the retina. 

What the eye does.—The purpose of an 
eye is to make an image of an object and 
throw it onto the retina. When we look at a 
tree, the eye makes a small image or photo¬ 
graph of the tree and places it on the retina. 
This is done by the cornea and lens. If it 
were not for them, we could not tell a tree 
from a barn, though we should still be able to 
tell daylight fro,m darkness. We could not 
see anything distinctly without the cornea 
and lens. 

Experiment 23.—Secure a small magnify- 
ing-gla ss , a reading-glass, or a pair of specta¬ 
cles used by some old person. These are all 
lenses. Hold the lens up near the white wall 
of a room, opposite a window. Vary the posi¬ 
tion of the lens till you get a small, clear image 


2 5 o SECOND BOOK OF PHYSIOLOGY 

of the window on the wall. Notice that the 
image is upside down, which is always the 
position of an image in the eye. Now, change 
the position so as to get a distinct image of a 
tree or house outside. 

This experiment may be done very nicely 
with lamps or candles at night. 

This shows what the cornea and lens do for 
the eye. 

Use of the iris.—The iris makes the eye 
very beautiful, but it is also very useful. The 
iris can make the pupil larger or smaller, and 
in that way it regulates the amount of light 
that gets into the eye. We cannot see well 
if the light is too strong or too dim. The 
pupil gets large when the light is dim and 
small when the light is bright. 

Experiment 24.—Look into a mirror and 
notice the size of the pupil of the eye. Shade 
the eyes with the hands or a screen and notice 
how the pupils increase in size. This experi¬ 
ment may be performed by suddenly turning 
the wick of a lamp up and down while you 


THE SPECIAL SENSES 


2 5 * 


look into a mirror, or you can easily experi¬ 
ment with the eyes of your friend. 

Notice that the pupil of a cat’s eye is a 
narrow slit, which is nearly closed in daytime 
but is wide open at night. 

Use of the lens.—We cannot see distinctly 
unless the image or picture of an object falls 
right on the retina. The lens in the eye is 
shaped like the lens in your magnifying-glass. 
Both sides are bulged out. But the lens in 
the eye is soft and can be made to bulge more 
or less whenever it is necessary. In this way 
the lens can be made to place the image on 
the retina. If it were not for the work of the 
lens, all objects would have to be at the same 
distance from the eye before we could see 
them clearly. You can see an object clearly 
at a distance of two, ten, or fifty feet, but you 
have to change the shape of the crystalline 
lens to do so. 

Experiment 25.—Look at a window so 
that you can distinctly see the sash or glass. 
Keep the eye in that position, and notice that 


252 SECOND BOOK OF PHYSIOLOGY 

you can at the same time see a tree or house 
beyond, but not distinctly. Now look at the 
tree or house so that you can see them dis¬ 
tinctly, and the window will be indistinct. This 
is all caused by a change in the shape of the 
lens. 

Near- and far-sighted.—The eyes of some 
people are defective. The lens cannot place 
the image on the retina of their eyes except 
at certain distances. Some can see clearly 
only objects that are near. They are said to 
be near-sighted. The defect can be corrected 
by wearing concave glasses. 

Others can see distinctly only objects that 
are far away. They are said to be far-sighted. 
This defect can be corrected by wearing con¬ 
vex glasses. . 

Even a perfect eye will become far-sighted 
as one grows older, and that is the reason 
nearly all old people wear convex glasses. 

How the eye is moved.—We can see an 
object distinctly only when we look straight at 
it. If the eyeballs could not be moved, we 


THE SPECIAL SENSES 


2 53 


would have to be constantly turning the head 
to keep the eyes straight towards an object. 
This would be very inconvenient. So the ball 
is provided with six muscles as shown in Fig. 
79. They may be made to contract and roll 



Fig. 79 - —Muscles of the eye. 1, 2, 3, 4, recti muscles; 4 is 
opposite 2 and cannot be seen in cut; 5, superior oblique muscle ; 6, 
pulley through which the tendon plays ; 7, inferior oblique muscle; 
8, optic nerve. 


the eye in any direction. This is a great ad¬ 
vantage in all the small movements of the eye. 
As in reading, the head may be held still and 
the eyes only moved. 

Sometimes these muscles do not hold the 



254 SECOND BOOK OF PHYSIOLOGY 


ball straight and in its proper position. If the 
inside muscle pulls too much on the ball the 
eye will be rolled inward. The person is then 
said to be cross-eyed or squint-eyed. A good 
oculist can correct this defect and straighten 
the eyes. 

The optic nerve.—An optic nerve runs 
from each eye to the brain. The retina is one 
end of this nerve spread out on the inside of 
the eyeball. The image or picture formed by 
the eye stops on the retina. From there a 
message is sent along the optic nerve to the 
brain. In that way the cerebrum finds out 
what kind of an image is on the retina. If 
the visual area shown in Fig. 75 should be in¬ 
jured, blindness would be the result, because 
no message from the eye could be received. 

Protection of the eye.—The eye is a very 
delicate organ and needs to be carefully pro¬ 
tected. The eyeballs are placed in a bony 
socket, so they are less liable to be injured by 
accident. 

The eyebrows, eyelids, and eyelashes are 


THE SPECIAL SENSES 


2 55 


on guard all the time to protect the eye from 
sweat, dust, insects, or other matter that might 
get into the eye. 

The front of the eyeball is always moist 
with tears to keep it clean and clear. 

Tears are made by glands which are found 
under the skin near the outer end of the eye- 



Fig. 8o.— The left eye, with a portion of the eyelids removed, to 
exhibit the lachrymal canals and sac. i, lachrymal canals; 2, com¬ 
mencement of these on the lachrymal papillae ; 4, edges of the eye¬ 
lids; 5, lachrymal sac; 6, internal palpebral ligament. 


brows. The tears are poured upon the eye at 
its outer corner and are spread out by wink¬ 
ing. At the inner corner of the eye, as shown 
in Fig. 80, the tears are gathered up by a tube 







256 SECOND BOOK OF PHYSIOLOGY 

and carried into the nose. Sometimes, as in 
crying, the tears come so fast that this tube 
cannot carry them away and they fall out upon 
the cheeks. 

Care of the eyes.—Every one wants to 
have good eyes and wants them to be good as 
long as possible, but some people use their 
eyes so badly that they do not seem to 
care whether they go blind or not. Here 
are a few common rules which should be fol¬ 
lowed : 

1. Do not read fine print. 

2. Do not read by a dim light or by direct 
sunlight. 

3. Do not read while riding on a moving 
train. 

4. Do not read while lying on a lounge or 
after going to bed. 

5. Do not bend over a book and look 
straight down when you read. Hold the book 
in front of you and about fourteen inches away. 
If you are near-sighted, it will be well to have 
glasses fitted to the eyes. 


THE SPECIAL SENSES 


257 


6. The light, if possible, should come over 
the left shoulder upon the work you are doing. 

7. If the eyes pain and smart when they 
are used, an oculist should be consulted at 
once before any serious injury is done. 

8. Avoid tobacco, for it irritates the eyes 
and sometimes affects the optic nerve so much 
that blindness is the result. 

9. Keep the whole body healthy and the 
eyes will share in it. 

The ear.—The ear is the organ of hearing. 
It does nothing but receive sounds and make 
a report of them to the brain. It is difficult 
to tell which is our most important sense organ, 
—the eye or the ear. Both are very important, 
and it is a great calamity to be either blind or 
deaf. 

The ear is composed of three parts called 
the external ear , middle ear , and the internal 
ear. 

The external ear is the part that can be seen 
on the outside of the head, called the pinna , 
and the canal leading in to the middle ear. 

17 


258 SECOND BOOK OF PHYSIOLOGY 

The pinna is made of cartilage, and stands out 
so as to catch the sound and direct it into the 
canal. 

The canal is guarded by hairs and a bitter 
wax which keep out dust and insects. The 
wax is secreted by wax- 
glands and poured into 
the canal 

The middle ear is 
the part marked t in 
Fig. 82. It is a cavity 
filled with air, and is 
shut off from the 
canal by a membrane 
marked tm . For this 
reason it is called the 
drum of the ear, and the 
membrane is called the 
drum-head. Another 
canal, marked eu, runs 
from the drum to the throat. It is called the 
Eustachian tube. 

In the upper part of the drum are three 
little bones marked h , a , and s. h is the 



L 


Fig. 81.—Pinna of ear. 
H y helix; C, concha; Z, 
lobe; E y entrance to auditory 
meatus. 


THE SPECIAL SENSES 


259 


hammer; a , the anvil ’ and j, the stirrup . The 
handle of the hammer is fastened to the drum- 



Fig. 82. —Diagram showing the relative position of the three parts 
of the ear. m, meatus; tm , tympanic membrane ; t, tympanum ; h, 
malleus; a , incus ; s, stapes ; o, oval window ; eu, Eustachian tube; 
sc, semicircular canals; v, vestibule ; c, cochlea ; F, fulcrum of the 
lever formed by the ossicles. 

head, and the stirrup is fastened to the inter¬ 
nal ear. 

The internal ear is an irregular cavity in the 
solid bone. It contains many winding pas¬ 
sages, all filled with a thin liquid which is 



260 SECOND BOOK OF PHYSIOLOGY 


nearly pure water. The three upper channels, 
marked sc, are called the semicircular canals. 
The coil, marked c, is called the cochlea , 
because it looks like a snail-shell. 

The nerve of hearing, called the auditory 
nerve, is distributed in the canals of the inter¬ 
nal ear, chiefly in the cochlea. 

The path of a sound.—The pinna catches 
the sound and directs it in through the canal 
marked m. It makes the drum-head vibrate, 
and the vibration is carried by the three little 
bones to a small window in the internal ear. 
There the stirrup vibrates back and forth and 
shakes the liquid in the internal ear. 

This disturbs the ends of the nerves in the 
cochlea, and they report the disturbance to 
the cerebrum. 

The cochlea is a very delicate and wonder¬ 
ful organ. All the sounds that we hear, and 
all the beautiful music which we enjoy, are 
sensations from the cochlea. 

Use of the semicircular canals.—The 

semicircular canals seem to be of no use in 


THE SPECIAL SENSES 261 

hearing ; but they are very useful in another 
way. They give to the mind its sense of 
equilibrium, or balance. By this sense we are 
able to walk or run without falling. This is 
done by the motion of the liquids in the canals 
whenever the head is moved. 

Care of the ear. —The Eustachian tube 
connects the throat and the middle ear. The 
purpose of this is to keep the air-pressure in¬ 
side the drum the same as it is on the out¬ 
side. Often when the throat is inflamed, this 
tube is partly or wholly closed. Then hear¬ 
ing is not distinct. Sometimes the inflamma¬ 
tion may extend into the middle ear and cause 
serious trouble. Such cases need careful 
treatment by a good physician. 

Sometimes ear-wax will collect on the drum¬ 
head and hearing will be dull. It can be re¬ 
moved by a doctor. The wax should not be 
picked out by means of a pin or other hard 
instrument. 

Insects sometimes crawl into the ear, and it 
may be very disagreeable to have them there, 


262 SECOND BOOK OF PHYSIOLOGY 


but they seldom do any harm. A little warm 
water or sweet oil poured into the ear will cause 
them to come out, or they may be taken out 
with proper instruments. 

A loud explosion near by is injurious to 
the ear. The shooting of cannon or the ex¬ 
plosion of large fire-crackers may break the 
drum-head of the ear. 

The sense of touch.—The sense of touch 
has been partly described in the chapter on 



Fig. 83.— Two tactile papillae from skin of finger. Touch corpuscle 
within and nerve-fibres below. 

the skin. This sense is next in importance to 
those of sight and sound. 







THE SPECIAL SENSES 


263 


The most important organ of touch is the 
tactile corpuscle , shown in Fig. 83. These 
are found in great numbers in the papillae of 
the palms and soles. One or more sensory 
nerve-fibres end in each one of them. 

Other small bulbs at the ends of sensory 
nerves are distributed throughout the whole 
skin. 

Sense of touch at different points of 
the body.—The sense of touch is quite 
acute on the ends of the fingers, and we 
use this sense to gain a great deal of infor¬ 
mation. 

By placing the fingers upon an object we 
can tell whether it is rough or smooth, fine or 
coarse, silk or wool, and so on. Those who 
buy dry-goods can tell the quality by the sense 
of feeling. 

Blind people read by running their fingers 
over raised letters. 

In a thousand ways we use the sense of 
touch to gain information. 

One of the important uses of the sense of 


264 SECOND BOOK OF PHYSIOLOGY 

touch in the skin is to inform the brain when¬ 
ever the body is touched. In this way the body 
is often saved from serious accidents and injury. 

The sense of touch is most acute on the 
tip of the tongue ; next, on the ends of the 
fingers ; next, on the lips ; and least of all on 
the back. 

Experiment 26. —Get a pair of compasses 
with blunt points, and a ruler divided into 
inches and parts of an inch. Place the com¬ 
passes so that both points touch the skin on 
some portion of the body, say on the back of 
the hand. Bring the points closer and closer 
together until you cannot tell whether there 
are two points or one. Then place the points 
on the ruler to see how far they are apart, 
make a record of this, and try a number of 
other places. You will probably find, for ex¬ 
ample, that on the ends of the fingers the 
separate points can be felt until they are only 
about one-eighth of an inch apart, while on 
your back they may be as much as two inches 
apart. 


THE SPECIAL SENSES 


265 


Experiment 27. —Blindfold some one and 
seat him on a chair. Touch him very lightly 
at various points on the body, and then ask 
him to place his finger on the exact spot where 
he was touched. 

This will show how accurately the brain can 
locate the point from which it received a sensa¬ 
tion of touch. 

Sense of smell. —The organ of smell is 
located in the upper part of the nostrils. 
This is the proper place for this organ, because 
the gas or fine particles which we smell are 
in the air. When we breathe, the air is drawn 
through the nostrils, and we detect any odor 
which the air contains. 

The nerve of smell is called the olfactory 
nerve. It ends in numerous branches in the 
nostrils, and reports to the brain any odor 
which it receives. 

In ordinary breathing the air does not come 
in contact with many of the nerves ; but by 
sniffing, the air is drawn up farther into the 
nostrils, and smelling is much more acute. 




266 SECOND BOOK OF PHYSIOLOGY 


Uses of the sense of smell. —The sense 
of smell gives us often a knowledge of the 
purity or impurity of the air. When we enter 
a close room that is poorly ventilated this sense 
will tell us that such air is not fit to breathe. 

It also helps us in the selection of food. 
The foul odor of rancid butter and decaying 
meat will be reported at once by the organ of 
smell. 

In some animals the sense of smell is the 
most important of the five, but in man the 
two senses, smell and taste, are the least used. 
They have, however, many important uses, and 
should be cared for and trained that they may 
be as useful as possible. 

The catarrhal condition of the mucous mem¬ 
brane of the nostrils is destructive to the organ 
of smell. 

The sense of taste. —The sense of taste 
is a guard placed at the gateway to the 
stomach, just as smell is a guard for the lungs. 

The organs of taste are located chiefly on 
the tongue. The surface of the tongue looks 


THE SPECIAL SENSES 


267 


rough because of the numerous papillae upon 
it. On the back of the tongue are seven 
large papillae. These contain the taste-cells , 
and nerves run from them to the brain. 

The taste-cells can distinguish sweet, sour, 
bitter, and salt substances. 

If the tongue is dry, there can be no sense 
of taste. Substances must be in solution be¬ 
fore they can get to the taste-cells. 

Experiment 28. —Wipe the tongue with a 
clean handkerchief or towel till it is quite dry. 
Then at once try to taste a lump of sugar or 
dry candy. There will be no taste until the 
tongue becomes moist again. Wipe the tongue 
again and try some dry salt. 

This experiment will show that a substance 
must be in solution before it can be tasted. 

Education of the taste sense. —The sense 
of taste may be cultivated till it becomes very 
acute and a safe guide in the selection of 
food ; but the organs of taste may be easily 
injured so that the sense becomes blunt. 


268 SECOND BOOK OF PHYSIOLOGY 


Tobacco and alcohol may so injure the taste- 
cells that scarcely any sense of taste remains. 

A delicate piece of machinery can be kept 
in good running order only when it is handled 
with intelligence and care. The same is true 
of the delicate organs of the human body. 

QUESTIONS. 

1. Name the special senses. 

2. Where do we see and hear ? 

3. Name several general sensations. 

4. Of what advantage are the special senses ? 

5. Describe the eye. 

6. Make a drawing of a section of an eye (Fig. 78) 
and name the parts. 

7. What does the eye do ? 

8. Of what use is the iris? 

9. Have you tried Experiments 23 and 24? 

10. What does the crystalline lens do? 

11. State what you found by trying Experiment 25. 

12. Explain what is meant by near-sighted and far¬ 
sighted. What kind of glasses should be used in each 
case? 

13. How is the eye moved ? Why is this needed ? 

14. What is the trouble when people are cross-eyed? 

15. How can we know that we are looking at a tree or 
a house ? 


THE SPECIAL SENSES 


269 


16. How are the eyes protected? 

17. Tell all you can about tears. 

18. Give several rules for the care of the eyes? 

19. What are the three parts of the ear? 

20. What is the use of the pinna? 

21. Describe the middle ear. Why is it called the 
drum ? 

22. Describe the internal ear. 

23. Describe the path of a sound from the pinna to 
the brain. 

24. What part of the internal ear is most important? 

25. What is the use of the semicircular canals? 

26. Give some rules for the care of the ear. 

27. Where is the sense of touch located? 

28. Of what use is the sense of touch? 

29. What part of the body did you find (Experiment 
26) to be most sensitive to touch? 

30. What is the olfactory nerve ? 

31. What are the uses of the sense of smell ? 

32. Where are the taste-cells located? Why? 

33. Have you tried Experiment 28? What did you 
find? 


CHAPTER XIII* 


TUBERCULOSIS 
I. THE EXCITING CAUSE 

Bacteria. —A great many diseases from 
which we may suffer are caused by the en¬ 
trance into our bodies and the growth there 
of very small forms of life, some of which are 
of an animal nature and others are forms of 
vegetable life. These small bodies are com¬ 
monly called “ germs,” but as this word is not 
definite, it is better to refer to them under 
their proper name. There are many different 
kinds of these vegetable forms which cause 
disease, but the principal kind is called the 
Bacterium ,—plural Bacteria . 

Size and shape. —Bacteria are so ex¬ 
tremely small that they cannot be seen except 


* Written by Dr. Louis Leroy, State Bacteriologist and Professor 
of the Practice of Medicine, College of Physicians and Surgeons, 
Memphis, Tenn. 

270 



TUBERCULOSIS 


271 


under a powerful microscope. It would take 
hundreds of them placed end to end to reach 
across a space as wide as a period on this 
page. In shape the bacterium which causes 
tuberculosis resembles a rod. See Fig. 35, 
page 131. 

Nature and growth. —There are many 
varieties of bacteria, most of which are not 
capable of doing us any harm, but some of 
them may produce disease, just as many kinds 
of plants are harmless while others are poi¬ 
sonous. Small as they are, each kind is 
always the same, and a bacterium which pro¬ 
duces a certain disease will always produce 
that disease and cannot produce any other. 
Hence we have bacteria which cause diph¬ 
theria, bacteria which cause typhoid fever, 
bacteria which cause cholera, and other bac¬ 
teria which cause tuberculosis. 

Bacteria multiply by division, that is to say, 
they grow in length and divide into parts, 
each part becoming a separate and distinct 
bacterium. These in turn multiply and thus 


2 7 2 SECOND BOOK OF PHYSIOLOGY 

it may be seen that they soon become very 
numerous. When supplied with plenty of 
air, warmth, and moisture, bacteria will grow 
rapidly. They can stand almost any amount 
of cold or drying without killing them, and if 
at any time they come in contact with a pre¬ 
disposed person or animal, they will regain 
their vitality and begin to grow, producing 
disease. Sunlight will kill them slowly, but 
heat and antiseptics will destroy them quickly. 

Tuberculosis. —When the bacteria of tu¬ 
berculosis are able to grow in the body, the 
person becomes ill and suffers from symptoms 
which vary according to the part of the body 
affected. The lungs are the organs which 
suffer more frequently from this disease than 
other parts of the body; and, when this is the 
case, the patient is said to have pulmonary 
tuberculosis ,—tuberculosis of the lungs, or, as 
it is commonly called, consumption. 

The bones and the joints are often affected 
by this disease, as is seen in hip-joint disease 
and hump-back. The disease sometimes af- 


TUBERCULOSIS 


273 


fects the intestines, coverings of the brain, or 
the skin, and less frequently any other organ 
of the body, so we must not think of tubercu¬ 
losis as a disease of the lungs only. 

Its prevalence. —The human race has 
always suffered from this disease. In the 
oldest remains that have ever been found, 
evidences of its ravages have sometimes been 
discovered, some of the bacteria having been 
found in the oldest mummies. To-day the 
disease is most universal, being found in every 
country on the earth. 

Its fatality. —Statistics show that about 
one-seventh of all deaths that occur in the 
world are caused by tuberculosis, which is now 
regarded as the greatest single cause of death 
among mankind. About one in every ten of 
the entire white race dies of it. Every year, 
in the United States, there are about two hun¬ 
dred thousand deaths from tuberculosis. That 
is, five hundred and forty-eight every day, or 
one death in every two and one-half minutes 
throughout the day and night continually. 


274 SECOND BOOK OF PHYSIOLOGY 

This appalling array of facts becomes still 
more important when we realize that nearly 
all this could have been avoided if every per¬ 
son had given even a little more attention to 
the means which will prevent the spread of 
bacteria. 

Neither age, sex, nor race is exempt.— 

At no age is a person exempt from this dread 
disease, but more cases occur between the 
ages of twenty and forty than at any other 
age, and a majority of these cases could 
have been avoided by proper attention to 
exercise and hygienic surroundings in the 
early years while the patients were grow¬ 
ing up. 

Men and women are about equally liable to 
the disease, but the different races are not at 
all equally susceptible. Tuberculosis has had 
as much to do with the extermination of the 
Indians as have the white man’s bullets, and 
to-day the negro race shows a death-rate two 
and one-half times as great as that of the 
white race. 


TUBERCULOSIS 


275 


Toxins.— As the bacteria grow in the body 
they make substances called toxins , which 
may be classed among the most poisonous 
substances in the world. It will be easier to 
understand how bacteria do this, if we re¬ 
member that, after all, they are but microscopic 
plants and that many of the larger plants that 
we know of also produce poison as they grow, 
or that common yeast, which is also a micro¬ 
scopic plant, when it grows in sugar, will 
produce alcohol, which is to some extent a 
poison. 

As the toxin is produced by the bacteria it 
is absorbed by the blood and carried through¬ 
out the body, poisoning it and producing 
weakness, fever, and other symptoms of the 
disease. The more bacteria there are and the 
more they spread, the more toxin will be pro¬ 
duced and the more the patient will be poi¬ 
soned, until finally he will no longer be able 
to endure it and he will die. This is generally 
the case with those persons who did not 
recognize the disease before it had gone too 
far. If they had known their true condition 


276 SECOND BOOK OF PHYSIOLOGY 


and had consulted a good doctor and followed 
his advice, they might have been cured. To 
prevent the disease from getting too great 
start we must know some of the early signs 
of trouble, be on our guard to recognize 
them and then give them immediate attention. 

The true cause of tuberculosis as set forth in the forego¬ 
ing section was unknown until 1865, when Dr. Villinin, of 
France, discovered that animals might be given the disease 
by inoculating them with particles of material taken from 
man or animals suffering with the disease, in this way show¬ 
ing the cause to be alive and capable of growing in the new 
animal. In spite of a great deal of study by scientific men, 
it was not until 1882 that Robert Koch was able to discover 
the bacteria of tuberculosis. 


2 . PREDISPOSING AND CONTRIBUTORY CAUSES 

Predisposing causes. —There are certain 
conditions of the body which make us liable 
to contract bacterial diseases, or make us 
unable to resist them if we are once af¬ 
fected. These are called predisposing causes y 
but no matter how many predisposing causes 
may exist, we will not contract the disease 


TUBERCULOSIS 


277 


unless we add to these the presence of bac¬ 
teria, which are the real or “ exciting cause!' 
Predisposing causes simply pave the way, or, 
in other words, prepare the soil for the bacteria. 

Heredity. —Years ago it was believed that 
tuberculosis was usually inherited, but we 
know now that it is only the tendency to the 
disease which consumptive parents transmit 
to their children, and that if such children are 
properly cared for, they will, in most cases, 
outgrow this tendency, and so strengthen their 
bodies as to be able to avoid the disease. 

Constitution. —It will be seen, then, that 
the constitution has much to do with our abil¬ 
ity to resist disease, but it is rather difficult 
to tell just what properties of the body are 
necessary to avoid consumption. Physical 
strength will not suffice, for while this is in 
some measure beneficial and of advantage, 
yet we know that many athletes fall victims to 
the disease in the prime of life. Anything 
that tends to increase our vigor and strength 


278 SECOND BOOK OF PHYSIOLOGY 


is of advantage, yet if we have a weak point 
anywhere in the body, that may be sufficient 
to permit some of the bacteria to gain a foot 
hold. We must not only maintain a high aver- 
age of general health, but we must guard the 
weak spots. For this reason we can see why 
chronic drinkers frequently fall victims to the 
disease and why persons addicted to the use 
of morphine, cocaine, or other drugs, seldom 
escape the disease for many years. 

Effects of other diseases. —It often hap¬ 
pens that the body is so weakened by other 
illnesses that it falls an easy victim to tuber¬ 
culosis ; and this is especially true after an at¬ 
tack of measles, influenza, or pneumonia, as 
well as any chronic cold, bronchitis, or irritation 
of the lungs. 

Adenoids. —Children sometimes suffer 
from growths, called adenoids , which are lo¬ 
cated in the extreme back of the nasal pas¬ 
sages. These growths obstruct the breathing 
passages, and lead to the bad habit of breath¬ 
ing through the mouth. This mouth-breathing 


TUBERCULOSIS 


279 


allows the cold air and dust to pass directly 
into the bronchial tube, and in this way bac¬ 
teria may gain an entrance into the irritated 
tonsils, adenoid growths, and inflamed throats, 
and through the lymphatics they may be con¬ 
veyed to deeper and more important struc¬ 
tures. Because adenoids increase the danger 
from consumption they should be attended to 
without delay. 

Scrofula. —Some children suffer from en¬ 
larged or swollen glands of the neck, com¬ 
monly called “kernels,” and sometimes “scrof¬ 
ula.” It has been found that in nearly all 
such cases the swelling is due to tubercle 
bacteria which have gained an entrance into 
the lymphatics, but have filtered out; and, 
stopped in their progress by these glands, 
they are setting up an inflammation in them. 
If this is not attended to the bacteria may 
make their way past these glands and be car¬ 
ried with the lymph to other parts of the body. 
Many cases of consumption have started in 
this way. 


280 SECOND BOOK OF PHYSIOLOGY 


Contributory causes. —Aside from the 
predisposing causes which exist within the 
body, there are causes resulting from environ¬ 
ment. These may properly be called contrib¬ 
utory causes , and they relate to the sanitary 
condition of homes, to occupations, to over¬ 
work, to exposure to wet and cold—in fact 
they include anything and everything that 
weakens the body and increases the liability 
to an attack. 

Localities. —Some localities favor the de¬ 
velopment of tuberculosis, as, for instance, 
those in which the air is laden with irritating 
limestone dust, or in which the air is damp 
and the temperature variable. All cities are 
worse than country districts, and the danger 
from consumption in them increases with the 
density of the population. 

Occupations. —Liability to contract this 
disease is greatly increased by those occu¬ 
pations which expose persons to irritating 
dust, as street sweepers, coal miners, stone 


TUBERCULOSIS 


2 8 r 


cutters, cotton spinners, and all persons work¬ 
ing in poorly ventilated factories. Indoor oc¬ 
cupations and those which compel persons to 
assume cramped positions furnish their full 
share of consumptives. 

Child labor. —In large cities the problem 
of child labor is one which demands and for¬ 
tunately is receiving a good deal of attention. 
Children under fourteen years of age are not 
able to stand hard, confining work such as 
they are ofttimes compelled to do in factories 
or mills. They should be allowed to devote 
all their strength and vitality to building up 
the body so as to develop into robust, healthy 
adults. While they may be able apparently 
to stand the hard work and close confinement, 
their vitality will be sapped and their systems 
so weakened as to make them more liable to 
disease. It has been found that large num¬ 
bers of children who work in mills and fac¬ 
tories contract tuberculosis and die at an 
early age. 

Children of tender years are sometimes 


282 SECOND BOOK OF PHYSIOLOGY 


overworked in the performance of household 
and other labor about the home. A reason¬ 
able amount of home work or outdoor work 
should be done by children, for while they are 
young they should learn to perform such 
duties, the knowledge and responsibility being 
an excellent training. But care must be taken 
that the child’s strength and vitality be not 
overtaxed, and that ample time be given for 
healthful play. 

Dust. —Another considerable source of 
danger is dust. Previously it has been shown 
how tuberculosis material may dry and be 
blown about as dust, and it is a fact that the 
dust of the streets, especially in cities, con¬ 
tains many bacteria. It has been repeatedly 
proved that by taking some of the dust from 
public places like theatres, churches, or other 
places of congregation, or from the street, a 
guinea-pig, rabbit, or other susceptible animal 
may be inoculated and in a short time (usually 
a month or two) the animal will contract tu¬ 
berculosis and die. 


TUBERCULOSIS 


283 


The same dust blows into dwelling houses 
and settles upon the furniture, curtains, and 
carpets, and if it be stirred up by sweeping or 
dusting, more or less may enter into the lungs 
and cause disease. 

Dwelling houses. —Within recent years 
much has been done to make more healthful 
homes, but in many cases there is yet much 
room for improvement. A dwelling house 
should be built where water will not collect 
beneath or around it. Wide streets are al¬ 
ways better than narrow ones, because they 
give more air and sunshine. Parts of the 
city remote from factories and large buildings 
generally have less smoke and dust in the air, 
and are therefore preferable. It would greatly 
increase the healthfulness of any town or city, 
if dwelling houses were not built too close to¬ 
gether. Separate houses are more desirable 
than double houses or flats, and basements for 
living in are the worst of all. 

The rooms should be light and airy, admit¬ 
ting a reasonable amount of sunlight and 


284 SECOND BOOK OF PHYSIOLOGY 

having as many windows as convenient for 
ventilation. Houses should be well heated so 
that they will be comfortable with the windows 
partly open to give ventilation and fresh air all 
the time. There should be plenty of good, 
pure drinking water at hand, and there should 
be good plumbing and ample provision for 
the disposal of waste matter. The sleeping 
rooms should be large enough to give to 
each person at least one thousand cubic feet 
of space. 

Before a house previously occupied by one 
who had consumption is again used as a 
dwelling place, it should be thoroughly dis¬ 
infected. The walls should be thoroughly 
scraped and repapered or painted, and the 
floors should be thoroughly scrubbed with an 
antiseptic solution, for there are on record 
many cases showing that after a house has be¬ 
come infected, one family after another has 
contracted the disease soon after moving into 
the house. The same precaution should be 
taken after a person suffering with consump¬ 
tion dies in or leaves the house. 


TUBERCULOSIS 


285 


3. HOW BACTERIA ARE SPREAD 

The sputum of consumptives. —The bac¬ 
teria of tuberculosis are practically unable to 
grow and increase in number in the outside 
world, so that about all the increase in num¬ 
ber must occur in animals and persons having 
the disease; therefore, if this terrible disease 
spreads it must be through discharges or ma¬ 
terial from animals or persons affected. To 
the careless expectoration of consumptives 
may be traced many cases of the disease. 

The sputum coughed up by any person 
suffering with an ordinary developed case of 
consumption is found to contain enormous 
numbers of bacteria. It has been estimated 
that such persons will throw off in this way, 
in the course of twenty-four hours, about 
seven billion bacteria. 

If this sputum be expectorated in the open, 
it will dry and form dust, which, blown about 
in the air, may be breathed into the lungs by 
a person susceptible to the disease and thus 
start it afresh. 


286 SECOND BOOK OF PHYSIOLOGY 


From what has just been said it may be 
easily seen that the consumptive who is care¬ 
less about spitting endangers the lives of 
others and at the same time he lessens his 
chances of recovery, for the bacteria thrown 
off by him may again enter his lungs and at¬ 
tack parts which before were healthy. 

Flies.—Always active in getting into any 
discharge or material containing bacteria, flies 
do much to spread disease, by carrying offen¬ 
sive and deadly material to our homes and 
depositing it upon the food we eat and in the 
milk and water we drink. Flies breed in all 
kinds of filth, but if our houses and streets 
are kept clean, they will have comparatively 
little chance to develop. Houses should be 
properly screened, especially kitchens and 
places where food is kept, if we would avoid 
this source of danger. 

Milk.—It has been found by investigation 
that when cows suffer from tuberculosis their 
milk contains the bacteria of consumption, and 


TUBERCULOSIS 


287 . 


that persons drinking such milk are liable in 
this way to contract the disease. As babies 
and children drink more milk than do grown 
persons, it may be seen that this becomes a 
greater source of danger to babies than to 
grown persons, and that it is dangerous and 
unwise to feed to babies milk which has come 
from unhealthy cows. To kill bacteria in milk 
it should be heated to 150 degrees Fahren¬ 
heit for ten minutes, and then quickly cooled 
and covered until it is used. 

Meats.— There is some danger, too, in eat¬ 
ing the meats from animals which had the dis¬ 
ease when slaughtered. All meat used for 
food should be thoroughly cooked so as to 
kill all bacteria in it, lest they get into the 
body and cause tuberculosis. 

Drinking cups, etc.— Great care should 
be taken in handling anything which a con¬ 
sumptive has had in his mouth. Drinking 
cups, water glasses, knives, forks, etc., should 
be thoroughly cleaned with boiling water or 


, 288 SECOND BOOK OF PHYSIOLOGY 


some disinfectant before again using them. 
For the same reason persons should avoid 
putting lead pencils or things of that kind into 
the mouth. 

Domestic animals. —Nearly all kinds of 
animals suffer from tuberculosis; guinea-pigs 
and rabbits are very susceptible, and in this 
climate monkeys seldom escape the disease 
for any length of time. Dogs and cats occa¬ 
sionally have it. If any of our pets grow thin 
and sickly, or have a cough, we should have 
them examined by a veterinary, because they 
can spread the disease to other animals or to 
persons in the household. Horses and cattle 
contract the disease quite frequently and thus 
become a source of great danger to man. 
Sheep and hogs sometimes suffer from the 
disease, but not nearly so often as do the 
other animals mentioned; and goats almost 
never contract the disease. 

We must remember, then, that people can 
give the disease to the lower animals and that 
these in turn can give it to people, so that we 


TUBERCULOSIS 


289 


must not only guard against it among our¬ 
selves, but must do what we can to protect 
our pets or domestic animals. 


4. HOW THE BODY DEFENDS ITSELF AGAINST 
AN ATTACK OF BACTERIA 

Nature’s protection.—As we have seen, 
in most cases of consumption the bacteria get 
into the body either by being breathed into 
the lungs, or less often by being taken with 
food or drink, or once in a great while they 
may get into a cut or an open sore of some 
kind. Considering all things, it would seem 
strange that anyone should escape contract¬ 
ing the disease, for it is very certain that all 
persons must every once in a while come in 
contact with, or breathe in, some of these 
germs which are so very numerous. 

Cilia.—Fortunately, the body has some 
very effective means of protecting itself, if it 
is in good health and has not been weakened 
in some way so as to make it unable to do so. 


19 


290 SECOND BOOK OF PHYSIOLOGY 

Before the air gets to the smaller air-sacs, it 
passes through the bronchial tubes, which con¬ 
stantly branch and become smaller and smaller 
as they get deeper into the lungs. These 
bronchial tubes are lined with a membrane 
covered with cells bearing very fine hair-like 
projections called cilia. These cilia, moist¬ 
ened and sticky from mucus, are constantly 
waving backwards and forwards. This wav¬ 
ing motion is not the same in both directions, 
the forward motion being strong and rapid 
and the backward motion slow, so that any 
fine particle which may lodge upon their sur¬ 
face will be carried upward toward the throat 
again. 

When we breathe in any dust most of it 
will adhere to the moist walls of the air-pas¬ 
sages, and then the cilia will at once start to 
pass the particles back to the throat, where 
they will be coughed up and spit out. But if 
there be too much dust for the cilia to throw 
off or if, as is often the case after a bad cold 
or pneumonia, some inflammation or injury 
has weakened the cells or killed some of them, 


TUBERCULOSIS 


291 


then this provision of nature may not be able 
to protect us from the evil effects of the dis¬ 
ease-laden dust. To avoid this state of af¬ 
fairs the throat and air-passages must be 
kept healthy and strong as possible, and if 
the throat should become sore, it should be 
cured at once so that it may not become 
chronic. 

White corpuscles and scar tissue.—If 

the tubercle bacteria should get into the air- 
sacs or find lodgement in the air-passages, they 
try to grow there and will irritate the lungs 
at that point, setting up a little inflammation. 
As a result of this inflammation the body will 
send more blood there, and, if healthy, the 
blood will contain substances which will over¬ 
come and kill the bacteria, thus preventing 
them from doing us harm. The white cor¬ 
puscles of the blood will collect around the 
spot as the result of the slight inflammation ; 
and, if only a few bacteria are present, may 
succeed in killing them. Some of the white 
corpuscles may be killed in their efforts to 


292 SECOND BOOK OF PHYSIOLOGY 


protect us, but when killed they set free sub¬ 
stances which in turn will kill the bacteria. 
If these means of defense fail through lack of 
strength the bacteria will continue to multiply 
and the inflammation will go on spreading, 
and the body will now begin to protect itself 
by building a wall of scar tissue around the 
spot affected, trying to wall in the bacteria, 
prevent their spreading, and starve them out. 
This is very often successful and the person 
may never know that he had ever been threat¬ 
ened with the disease. 

Owing to a weakened condition of the 
body, it is, in many cases, unable by these 
means to remove or to destroy the bacteria. 
They continue to grow and multiply more 
and more, and spread farther and farther, 
until a large part of the lungs is affected and, 
as a result of their irritation and the en¬ 
trance of other bacteria, parts of the lungs 
die and are destroyed, leaving holes or cav¬ 
ities. 


TUBERCULOSIS 


2 93 


5. TUBERCULOSIS MAY BE CURED 

At one time it was thought that consump¬ 
tion was always a fatal disease, but it is now 
known that sometimes even the worst cases 
may get well, and that if the disease is recog¬ 
nized early, most cases can be cured. 

It should be remembered that consumpdon 
is a most insidious disease, stealing upon its 
victim and ofttimes doing great damage ere 
its presence is suspected. This being the 
nature of the disease, the greater is the neces¬ 
sity for persons to be on the alert to detect 
the first indications of its presence; and if a 
person has the least suspicion that he has con¬ 
tracted the disease he should immediately con¬ 
sult a physician, for every day of delay dimin¬ 
ishes his chance of recovery. 

Early signs of consumption. —Some of 
the earliest signs that consumption is develop¬ 
ing are a gradual loss of weight and strength, 
and a slight fever in the afternoon without 
apparent cause. Loss of appetite or indiges- 


294 SECOND BOOK OF PHYSIOLOGY 

tion with a general tired feeling is the first 
sign in other cases. A chronic cough, or a 
cough early in the morning, which lasts some 
time and does not tend to get better, is always 
suspicious, but it must be borne in mind that 
very many cases of tuberculosis are without 
any cough until the disease is pretty well 
established. 

Medicinal treatment. —The treatment of 
consumption so far as medicines are concerned 
may be safely left to a physician. Avoid 
patent medicines and all advertised cures, as 
these frequently contain opium and other in¬ 
jurious drugs. Much medicine is not needed, 
the treatment being largely sanitary. The 
person who indulges the hope of being cured 
of consumption must conform to his physi¬ 
cian’s advice in every particular. The follow¬ 
ing instructions will be very helpful if strictly 
observed: 

Disposal of sputum. —Tuberculosis is not 
directly contagious as are smallpox or measles, 


TUBERCULOSIS 


2 95 


from simply being near a case, but if a person 
having consumption is at all careless in cough¬ 
ing or spitting, he may spread the disease to 
his friends and family and lessen his chances 
of recovery. When it is necessary for him to 
expectorate he should use a paper napkin or 
rag which can be burned before it becomes 
dry, and which can be kept away from the flies. 
Metal or paper pocket flasks are made for 
this purpose, and they may be burned up or 
sterilized when necessary. If cuspidors are 
used they should contain an antiseptic solu¬ 
tion like weak carbolic acid (six teaspoonfuls 
to a pint of water), and these should be 
cleaned daily. He should never swallow any 
of the material he coughs up, because in that 
way the disease maybe carried to. the stomach 
or the intestines. When coughing or sneezing, 
he should hold a handkerchief to his mouth, as 
the fine spray produced may contain bacteria, 
which should not be thrown into the air. For 
a similar reason he should not wear a beard 
or moustache, and should keep his face clean 
by frequent washing with soap and water. 


296 SECOND BOOK OF PHYSIOLOGY 


Dress.— He should dress comfortably, but 
not so heavily as to make him perspire and 
take cold. Tight collars, corsets, or any other 
clothing that would tend to interfere with free 
breathing should be absolutely avoided. 

Diet. —His diet should be full and nourish¬ 
ing, consisting largely of such things as milk, 
buttermilk, eggs, and beef. Heavy, indiges¬ 
tible food must be avoided, and fried dishes 
should be used as little as possible. Alco¬ 
holic drinks should not be used, and he should 
not smoke. 

Fresh, pure air. —A person having con¬ 
sumption should stay in the open air as much 
as possible, for fresh air and sunlight do more 
towards curing the disease than any amount 
of medicine. 

The rather popular idea that night air is 
any worse than or different from day air is en¬ 
tirely erroneous, for the air itself is just the 
same, and so long as the person is protected 
from dew he derives as much benefit from 


TUBERCULOSIS 


297 



night air as he would from the air in the 
daytime. 


Courtesy of The Kny-Scheerer Co., New York. 

Fig. 84.—Indoor sleeping-tent—raised. 

If he sleeps in the house, all the windows 
should be open so as to avoid draughts, for 
with one window open or partly open, a 






















298 SECOND BOOK OF PHYSIOLOGY 



draught may be produced which would give 
him a cold, whereas if they are all open he 
does not run this risk. 

It is a well-known fact that soldiers, cow¬ 
boys, and persons living in the open air rarely 


Courtesy of The Kny-Scheerer Co., New York. 

Fig. 85.—Indoor sleeping-tent—in use. 

if ever take cold, unless they happen to spend 
some time indoors. Of course, if the weather 
is very cold or it is raining so that the room 
would become wet or damp the windows 
should be protected with awnings or should 














TUBERCULOSIS 


299 


be partly closed, or the room may be heated 
sufficiently to take off the chill. 

In winter and in cold climates it is a good 
plan to have next to the sleeping room a warm 
room in which to dress, so as to avoid getting 
chilled. 

An excellent device which is being used 
quite extensively is the indoor sleeping tent. 
It consists simply of an arrangement like an 
awning, which fits in an open window and 
comes down over the head of the bed, the 
latter being placed alongside the window. It 
covers the head and shoulders of the person 
while the remainder of his body is in the warm 
room. In this way the person’s head is prac¬ 
tically outdoors and he has fresh, pure air to 
breathe all the time. By removing his head 
from under the awning he is in a warm room 
where he can dress without taking cold. 

Modern houses and tents. —A great 
many of the more modern houses are now 
being built with upstairs, screened porches for 
sleeping, with dressing room alongside. In 


3 oo SECOND BOOK OF PHYSIOLOGY 


some of the large cities, where tenement 
houses abound, and where the population is 
so dense that to get fresh air is otherwise im¬ 
possible, splendid results have been obtained 
with tuberculosis patients by* having them 
sleep on the fire escape or on the roof. Along 
the seacoast many excellent protected out¬ 
door sleeping places have been arranged on 
some of the long piers, and these have been 
instrumental in curing many cases of tuber¬ 
culosis. 

One of the very best sleeping quarters for 
persons predisposed is a tent, which should 
have a raised floor so constructed as to remain 
dry even in rainy weather. The canvas, being 
porous, permits a free and constant circulation 
of air without draughts. Except in dense 
parts of a city, room for such tent can always 
be found. 

As we can never tell just who may be pre¬ 
disposed to the disease—and many are predis¬ 
posed who never suspect it—it is a good thing 
for all persons to spend as much time as pos¬ 
sible in the open air. 


TUBERCULOSIS 


3 QI 


Living room of the consumptive. —The 

room of one suffering from tuberculosis should 
be light and airy, and contain as little as pos¬ 
sible of the things which collect dust, such as 
curtains, draperies, etc. Carpets, rugs, and 
bedding which he has used should frequently 
be aired and occasionally disinfected. 

When cleaning or sweeping the room care 
should be taken not to stir up the dust. To 
avoid this, carpets and rugs should not be 
swept with a broom, but with a carpet sweeper. 
When sweeping carpets moist tea leaves may 
be used to advantage, as also may paper cut 
into small pieces and moistened. These scat¬ 
tered over carpets and rugs will catch much of 
the dust and prevent its getting into the air. 
There are several inexpensive preparations of 
the nature of sawdust which may be used over 
and over again. These are slightly oily but 
they do not stain the carpets. On bare floors 
moist sawdust can be scattered and then 
swept up very conveniently. 

In dusting, use a slightly moistened cloth 
so that the dust may be collected, instead of 


3° 2 


SECOND BOOK OF PHYSIOLOGY 


being blown into the air, as it is sure to be if 
a feather duster be used. 

The best thing for removing dust from car¬ 
pets, rugs, walls, furniture, etc., is the Vacuum 
Cleaner, a recently patented device, which 
gathers up all dust into a reservoir, whence 
it is taken and buried or burned. 

Change of climate. —Consumptive pa¬ 
tients are often advised to go away to some 
distant place to recuperate their wasting ener¬ 
gies, and many of them do go, and return 
much improved, if not wholly cured. This 
change is due, not so much to a change of cli¬ 
matic conditions, as to the fact that while 
away from home they spent much of the time 
outdoors, where pure, fresh air and sunshine 
were given a chance to do good. 

The fact is that pure, fresh air and sunshine, 
together with judicious dieting, careful exer¬ 
cise, good, restful sleep, and the avoidance of 
everything that will in any measure impair the 
general health or aggravate the disease, will 
be beneficial in any climate. Unless a person 
has sufficient money to pay his expenses at a 


TUBERCULOSIS 303 

good sanitarium where he can get constant 
and careful attention of good physicians and 
competent nurses, home is the best place for 
one suffering with tuberculosis. The minis¬ 
trations of loving, sympathetic friends are in¬ 
estimable. 


6 . SUMMARY 

Every person having tuberculosis should 
observe strictly and conscientiously the fol¬ 
lowing brief directions. 

1. As you value your life and the lives of 
others, be sure to destroy all sputum, either 
by burning or by using antiseptics. 

2. Keep yourself, your room, and your bed¬ 
ding perfectly clean. Occasionally disinfect 
your room. 

3. During waking hours spend much time 
in the open air and the sunlight, avoiding 
dampness and protecting your head from the 
hot rays of the sun. 

4. See that your sleeping room is constantly 
supplied with fresh, pure air, but avoid 
draughts and dampness. 


304 SECOND BOOK OF PHYSIOLOGY 


5. Aim to get eight to ten hours of restful, 
refreshing sleep every day. 

6. Eat freely of plain, nourishing food, but 
avoid everything that causes uneasiness or 
gives you indigestion. 

7. Exercise freely, but do not carry it to the 
point of fatigue or exhaustion. 

8. Do not smoke, and avoid the use of alco¬ 
holic drinks. 

9. Do not kiss any one on the mouth, and 
see that everything you use in your mouth is 
sterilized before it is again used, either by 
yourself or by any other person. 

10. Take medicine only on the advice of 
your physician, and if he should advise you 
concerning exercise, diet, clothing, or any 
matter relating to sanitation, follow his in¬ 
structions to the letter. 

11. Avoid all extremes ; cultivate a cheerful, 
hopeful spirit; and never indulge in vicious 
thoughts. 


TUBERCULOSIS 


3°5 


7. RULES FOR PREVENTION OF TUBERCULOSIS 

Dr. Knopf of New York has prepared some 
“Rules for school children to prevent tuber¬ 
culosis,” which are so comprehensive that 
they may be presented here : 

“ Every child and adult can help fight con¬ 
sumption. School children can be helpful by 
complying with the following rules: Do not 
spit, except into a spittoon, a piece of cloth, 
or handkerchief used for that purpose alone. 
On your return home have the cloth burned 
by your mother, or the handkerchief put into 
water until it is ready for the wash. 

“ Never spit on a slate, floor, playground, 
or sidewalk. 

“ Do not put your fingers into your mouth. 

“ Do not pick your nose or wipe it on your 
hand or sleeve. 

“ Do not wet your fingers in your mouth 
when turning the leaves of books. 

“ Do not put pencils into your mouth or 
wet them with your lips. 

“ Do not hold money in your mouth. 


20 


3 o6 SECOND BOOK OF PHYSIOLOGY 

“ Do not put pins into your mouth. 

“ Do not put anything into your mouth 
except food and drink. 

“ Do not swap apple cores, candy, chewing 
gum, half-eaten food, whistles, bean blowers, 
or anything that has been in the mouth of 
another. 

“ Peel or wash your fruit before eating it. 

“ Never sneeze or cough in a person’s face. 
Turn your face to one side or hold a handker¬ 
chief before your mouth. 

“ Keep your face, hands, and finger nails 
clean. Wash your hands with soap and water 
before each meal. 

“ When you do not feel well, have cut your¬ 
self, or have been hurt by others, do not be 
afraid to report to the teacher. 

“Keep yourself just as clean at home as 
you do at school. 

“ Clean your teeth with a toothbrush and 
water, if possible after each meal; but at least 
on getting up in the morning, and on going to 
bed at night. 




TUBERCULOSIS 


3°7 


“ Do not kiss any one on the mouth or 
allow any one to do so to you.” 

To these might be added, eat regularly and 
avoid rich foods or overloading your stomach 
between meals. Avoid getting too tired or 
exhausted from anything. Go to bed at reg¬ 
ular hours, and get at least eight hours’ sleep, 
leaving a window up for ventilation. Spend 
as much time as you can outdoors. Do not 
cramp the lungs and organs of digestion by 
standing, sitting, or walking in a stooped posi¬ 
tion. Stand, sit, and walk erect, and occasion¬ 
ally inflate the lungs fully by taking deep 
breaths in the open air. Avoid all dusty 
places in which the air is musty or impure. 
Do not think it is apt or manly to use tobacco 
or alcohol while growing up, for what a man 
who has reached full development might possi¬ 
bly be able to endure will prevent children 
from attaining as fine development of mind 
and body as they could have had, had they let 
it alone, and many a child has gone to an un¬ 
necessary and untimely grave from the use of 
these things, who would have avoided con- 


308 SECOND BOOK OF PHYSIOLOGY 


tracting tuberculosis had he realized the injury 
he was doinor himself. 

While it is true that most cases of consump¬ 
tion can be cured if we take them early 
enough, still it is such an insidious disease 
that it will often get too strong a hold before 
it is corrected or recognized, and if we all 
would make it our business through life to 
pay attention to the prevention of the disease, 
and if each would contribute his share, it would 
be but a few years, comparatively, before the 
disease would cease to exist, instead of being, 
as it now is, a disease which kills more people 
than any other single cause, so as to be called 
“The Great White Plague.” 

QUESTIONS. 

1. What are bacteria ? Size and shape ? 

2. Tell of the nature and growth of the bacteria which 
cause tuberculosis. 

3. What is tuberculosis ? 

4. Tell of the prevalence of tuberculosis. 

5. Cite some facts to show its fatality. 

6. How does tuberculosis affect persons of different ages, 
the sexes, and the races of mankind ? 


TUBERCULOSIS 


309 


7. What are toxins ? 

8. What are predisposing causes ? 

9. Is tuberculosis hereditary ? 

10. What can you say concerning the constitution of a 
person as to its power to resist disease ? 

11. How do other diseases predispose a person to tuber¬ 
culosis ? 

12. Effect of adenoids. Scrofula. 

13. What are contributory causes ? 

14. What localities and occupations contribute toward 
consumption ? 

15. What of child labor ? 

16. What can you say of the dust of the streets, of 
churches, theatres, etc? 

17. Tell of dwelling houses—their location, construction, 
and disinfection. 

18. Tell of the sputum of the consumptive. 

19. Tell of flies as agents in the spread of disease. 

20. What of milk and meats from diseased animals ? 

21. How should drinking cups, water glasses, knives, 
forks, etc., used by consumptives be cleansed? 

22. Tell how domestic animals may become a source of 
danger. 

23. What are cilia and how do they protect us from 
disease ? 

24. How do white corpuscles protect the body ? 

25. What about scar tissue ? 

26. Can tuberculosis be cured ? 

27. Name the early signs of consumption. 


3 io SECOND BOOK OF PHYSIOLOGY 

28. Tell of medicinal treatment. 

29. How should the sputum be disposed of? 

30. How should a consumptive dress ? 

31. What should he eat ? 

32. What can you say of fresh, pure air as an agent in 
the cure of consumption ? 

33. Where should a consumptive sleep ? 

34. Describe the indoor tent. 

35. Tell how to care for the living room of a consumptive 
—how it should be furnished, swept, dusted, and disinfected. 

36. What of a change of climate ? 

37. Repeat the rules laid down for the guidance of those 
suffering from tuberculosis. 

38. Repeat Dr. Knopf’s rules for school children. 

39. Repeat other important rules. 




A 

Abdomen, 53 
Adam’s apple, 114 
Air in lungs, 122 
Air-sacs, 119 
Albumin, 10, 16 
Alcohol, 

amount in drinks, 75 
appetite for, 74 
as a food, 39 

as a source of warmth, 239 
effect on arteries, 105 
effect on athletes, 182 
effect on breathing, 136 
effect on digestion, 71 
effect on heart, 104 
effect on muscle, 179 
effect on nervous system, 236 
effect on organs of excretion, 
206 

effect on workmen, 181 
moderate use of, 73 
nature of, 35 
source of, 33 
uses of, 237 
Amoeba, 12 


INDEX 

* 

Amount of food, 31 
Animals and vegetables, 7 
Aorta, 90 
Argon, 124, 126 
Arteries, 89 
Auricles, 85 

B 

Beer, 37 
Biceps, 171 
Bicuspids, 48 
Bile, 60 
Bones, 

care of, 159 
composition of, 155 
kinds, 143 

of arm and hand, 151 
of leg and foot, 153 
strength of, 15b 
Brain, 211 
Bread, 30 
Breathing, 135 
Bronchi, 117 
Bronchial tubes, 118 

C 

Canals in bone, 158 


3 11 



3 12 


INDEX 


Canines, 48 
Capacity of lungs, 122 
Capillaries, 90 
Carbon dioxide, 126 
Cardiac orifice, 57 
Cells, 9 to 16 
Cerebellum, 215 
Cerebrum, 213 
Chewing food, 68 
Chyle, 61 
Chyme, 58 
Cider, 35 

Cilia, 12, 113, 118 
Circulation of blood, 79, 100 
effect of exercise on, 104 
organs of, 83 
Clothing, 195 
Color of skin, 189 
Combustion, in 
Composition of air, 124 
of the body, 14, 16 
Consumption of the lungs, 131, 
270 

Convolutions of brain, 214 
Cooking, 32 
Corn, 30 
Cranium, 143 

names of bones, 143 

D 

Dentine, 49 
Diaphragm, 53, 121 


Digestion, 43 
in the mouth, 46 
organs of, 44 
Dust, 129 

E 

Ear, 257 
care of, 261 
Eating, 20, 68 
Enamel, 48 
Epidermis, 188 
Excretion, 201 
Excretory organs, 204 
Exercise, 177 
Exhalation, 122 
♦Expired air, 128 
Eye, 248 
care of, 256 
parts of, 248 
Eye-muscles, 253 

F 

Far-sighted, 252 
Fat, 30 
cells, 190 

Fatigue of brain, 232 
Fermentation, 33 
Food, 22 
kinds of, 23 
of the brain, 231 

G 

Gall-bladder, 60 



INDEX 


3i3 


Gastric juice, 57 
Glands, 45 
Glottis, 114 

H 

Habit, 229 
Hair, 195 
Heart, 84 
cavities of, 85 
valves of, 87 
work of, 102 

I 

Impure air, 128 
Incisors, 48 
Inhalation, 120 
Intestine, 59 
Involuntary muscles, 173 

J 

Joints, 161 

K 

Kidneys, 205 
Kinds of food, 23 

L 

Larynx, 114 
Life, 6 

Lifeless matter, 5 
Ligaments, 163 
Liver, 60, 80 
use of, 82 
Lungs, 119 


M 

Matter, 5 

Medulla oblongata, 216 
Mixed diet, 31 
Motor areas of brain, 224 
nerves, 217 

Mucous membrane, 44 
Mucus, 45 
Muscles, 167 
development of, 176 
of eye, 253 
of face and head, 174 
skill of, 179 
structure of 173 

N 

Nails, 196 
Near-sighted, 252 
Nerve-cell, 210 
Nerve endings, 220 
Nerves, 216 
Nervous system, 209 
Nitrogen, 125 
Nostrils, 113 
Nucleus, IO 

O 

(Esophagus, 54 
Opium, 241 
Organ, 15 
Oxygen, 109, 125 



3 1 4 


INDEX 


P 

Pancreatfc juice, 60 
Papillae of skin, 190 
Patent medicines, 76 
Pericardium, 85 
Periosteum, 158 
Permanent teeth, 47 
Perspiration, 192 
Pharynx, 52 
Physiology, 9 
Pleura, 120 
Pores, 191 
Portal vein, 100 
Proteid, 23, 29 
Pulmonary artery, 90 
tuberculosis, 272 
Pulse, 99 
Pyloric orifice, 57 

R 

Red corpuscles, 94 
Reflex action, 227 
Respiration, 109 
organs of, 112 

S 

Saliva, 50 

experiments with, 51, 52 
Semiciicular canals, 260 
Sensory areas of brain, 224 
nerves, 217 
Skeletal muscles, 168 


Skeleton, 142 
Skin, 187 
Sleep, 233 
Small intestine, 59 
Smell, 265 
Special senses, 246 
Spinal column, 144 
cord, 218 
nerves, 219 
Starch, 23, 29 
Sternum, 154 
Stomach, 56 
care of, 70 
Strong drinks, 38 
Structure of teeth, 48 
Suture, 143 
Swallowing, 54, 55 
Sweat as a regulator of heat, 
193 

Sweat-glands, 191 
Sympathetic nerves, 221 
Synovial fluid, 164 

T 

Tartar, 69 
Taste, 266 
Tears, 255 
Teeth, 46 
care of, 68 
kinds of, 48 
structure of, 48 
use of, 49 




INDEX 


Temporary teeth, 47 
Tendon, 169 
Test of life, 6 
Thoracic duct, 83 
Thorax, 53 
Tobacco, 76 

effect on circulation, 106 
effect on digestion, 76 
effect on lungs, 138 
effect on muscles, 183 
effect on the nervous system, 
242 

Touch, 262 
Trachea, 117 
True skin, 188, 190 
Tuberculosis, 270 


V 

Valves, 86 
Veins, 91 
Ventilation, 132 
Ventricles, 85 
Vertebra, 144 
Villi, 61 

Vocal cords, 114, 115 
Voluntary muscles, 172 

W 


Water, 25, 28 
Wells, 26 
Wheat, 29 

White corpuscles, 14, 96 


THE END 


















































































































































































































































































































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